%================================================================ % LaTeX file with prefered layout for H1 paper drafts % use: dvips -D600 file-name %================================================================ \documentclass[12pt]{article} \usepackage{epsfig} \usepackage{graphicx} \usepackage{amsmath} \usepackage{hhline} \usepackage{amssymb} \usepackage{times} \usepackage{cite} \renewcommand{\topfraction}{1.0} \renewcommand{\bottomfraction}{1.0} \renewcommand{\textfraction}{0.0} \newlength{\dinwidth} \newlength{\dinmargin} \setlength{\dinwidth}{21.0cm} \textheight23.5cm \textwidth16.0cm \setlength{\dinmargin}{\dinwidth} \setlength{\unitlength}{1mm} \addtolength{\dinmargin}{-\textwidth} \setlength{\dinmargin}{0.5\dinmargin} \oddsidemargin -1.0in \addtolength{\oddsidemargin}{\dinmargin} \setlength{\evensidemargin}{\oddsidemargin} \setlength{\marginparwidth}{0.9\dinmargin} \marginparsep 8pt \marginparpush 5pt \topmargin -42pt \headheight 12pt \headsep 30pt \footskip 24pt \parskip 3mm plus 2mm minus 2mm %===============================title page============================= \begin{document} % The rest \newcommand{\pom}{{I\!\!P}} \newcommand{\reg}{{I\!\!R}} \newcommand{\slowpi}{\pi_{\mathit{slow}}} %\newcommand{\gevsq}{\mathrm{GeV}^2} \newcommand{\fiidiii}{F_2^{D(3)}} \newcommand{\fiidiiiarg}{\fiidiii\,(\beta,\,Q^2,\,x)} \newcommand{\n}{1.19\pm 0.06 (stat.) \pm0.07 (syst.)} \newcommand{\nz}{1.30\pm 0.08 (stat.)^{+0.08}_{-0.14} (syst.)} \newcommand{\fiidiiiful}{F_2^{D(4)}\,(\beta,\,Q^2,\,x,\,t)} \newcommand{\fiipom}{\tilde F_2^D} \newcommand{\ALPHA}{1.10\pm0.03 (stat.) \pm0.04 (syst.)} \newcommand{\ALPHAZ}{1.15\pm0.04 (stat.)^{+0.04}_{-0.07} (syst.)} \newcommand{\fiipomarg}{\fiipom\,(\beta,\,Q^2)} \newcommand{\pomflux}{f_{\pom / p}} \newcommand{\nxpom}{1.19\pm 0.06 (stat.) \pm0.07 (syst.)} \newcommand {\gapprox} {\raisebox{-0.7ex}{$\stackrel {\textstyle>}{\sim}$}} \newcommand {\lapprox} {\raisebox{-0.7ex}{$\stackrel {\textstyle<}{\sim}$}} \def\gsim{\,\lower.25ex\hbox{$\scriptstyle\sim$}\kern-1.30ex% \raise 0.55ex\hbox{$\scriptstyle >$}\,} \def\lsim{\,\lower.25ex\hbox{$\scriptstyle\sim$}\kern-1.30ex% \raise 0.55ex\hbox{$\scriptstyle <$}\,} \newcommand{\pomfluxarg}{f_{\pom / p}\,(x_\pom)} \newcommand{\dsf}{\mbox{$F_2^{D(3)}$}} \newcommand{\dsfva}{\mbox{$F_2^{D(3)}(\beta,Q^2,x_{I\!\!P})$}} \newcommand{\dsfvb}{\mbox{$F_2^{D(3)}(\beta,Q^2,x)$}} \newcommand{\dsfpom}{$F_2^{I\!\!P}$} \newcommand{\gap}{\stackrel{>}{\sim}} \newcommand{\lap}{\stackrel{<}{\sim}} \newcommand{\fem}{$F_2^{em}$} \newcommand{\tsnmp}{$\tilde{\sigma}_{NC}(e^{\mp})$} \newcommand{\tsnm}{$\tilde{\sigma}_{NC}(e^-)$} \newcommand{\tsnp}{$\tilde{\sigma}_{NC}(e^+)$} \newcommand{\st}{$\star$} \newcommand{\sst}{$\star \star$} \newcommand{\ssst}{$\star \star \star$} \newcommand{\sssst}{$\star \star \star \star$} \newcommand{\tw}{\theta_W} \newcommand{\sw}{\sin{\theta_W}} \newcommand{\cw}{\cos{\theta_W}} \newcommand{\sww}{\sin^2{\theta_W}} \newcommand{\cww}{\cos^2{\theta_W}} \newcommand{\trm}{m_{\perp}} \newcommand{\trp}{p_{\perp}} \newcommand{\trmm}{m_{\perp}^2} \newcommand{\trpp}{p_{\perp}^2} \newcommand{\alp}{\alpha_s} \newcommand{\alps}{\alpha_s} \newcommand{\sqrts}{$\sqrt{s}$} \newcommand{\LO}{$O(\alpha_s^0)$} \newcommand{\Oa}{$O(\alpha_s)$} \newcommand{\Oaa}{$O(\alpha_s^2)$} \newcommand{\PT}{p_{\perp}} \newcommand{\JPSI}{J/\psi} \newcommand{\sh}{\hat{s}} %\newcommand{\th}{\hat{t}} \newcommand{\uh}{\hat{u}} \newcommand{\MP}{m_{J/\psi}} %\newcommand{\PO}{\mbox{l}\!\mbox{P}} \newcommand{\PO}{I\!\!P} \newcommand{\xbj}{x} \newcommand{\xpom}{x_{\PO}} \newcommand{\ttbs}{\char'134} \newcommand{\xpomlo}{3\times10^{-4}} \newcommand{\xpomup}{0.05} \newcommand{\dgr}{^\circ} \newcommand{\pbarnt}{\,\mbox{{\rm pb$^{-1}$}}} \newcommand{\gev}{\,\mbox{GeV}} \newcommand{\WBoson}{\mbox{$W$}} \newcommand{\fbarn}{\,\mbox{{\rm fb}}} \newcommand{\fbarnt}{\,\mbox{{\rm fb$^{-1}$}}} % % Some useful tex commands % \newcommand{\qsq}{\ensuremath{Q^2} } \newcommand{\gevsq}{\ensuremath{\mathrm{GeV}^2} } \newcommand{\et}{\ensuremath{E_t^*} } \newcommand{\rap}{\ensuremath{\eta^*} } \newcommand{\gp}{\ensuremath{\gamma^*}p } \newcommand{\dsiget}{\ensuremath{{\rm d}\sigma_{ep}/{\rm d}E_t^*} } \newcommand{\dsigrap}{\ensuremath{{\rm d}\sigma_{ep}/{\rm d}\eta^*} } % Journal macro \def\Journal#1#2#3#4{{#1} {\bf #2} (#3) #4} \def\NCA{\em Nuovo Cimento} \def\NIM{\em Nucl. Instrum. Methods} \def\NIMA{{\em Nucl. Instrum. Methods} {\bf A}} \def\NPB{{\em Nucl. Phys.} {\bf B}} \def\PLB{{\em Phys. Lett.} {\bf B}} \def\PRL{\em Phys. Rev. Lett.} \def\PRD{{\em Phys. Rev.} {\bf D}} \def\ZPC{{\em Z. Phys.} {\bf C}} \def\EJC{{\em Eur. Phys. J.} {\bf C}} \def\CPC{\em Comp. Phys. Commun.} %%%%%%%%%%%%% my new commands %%%%%%%%%%%%%%%% \newcommand{\be}{\begin{equation}} \newcommand{\ee}{\end{equation}} \newcommand{\ba}{\begin{eqnarray}} \newcommand{\ea}{\end{eqnarray}} \begin{titlepage} %\begin{center} %{\it {\large version 1.08 of \today}} \\[.3em] % \begin{small} % \begin{tabular}{llrr} % %Submitted to & \multicolumn{3}{r}{\footnotesize Electronic Access: {\it http://www-h1.desy.de/h1/www/publications/conf/conf\_list.html}} \\[.2em] \hline % %Submitted to & \multicolumn{3}{r}{\footnotesize {\it www-h1.desy.de/h1/www/publications/conf/conf\_list.html}} \\[.2em] \hline % Submitted to & & & % %\epsfig{file=/h1/www/images/H1logo_bw_small.epsi,width=2.cm} \\[.2em] \hline % \epsfig{file=H1logo_bw_small.epsi,width=2.cm} \\[.2em] \hline % \multicolumn{4}{l}{{\bf } }\\ % & Abstract: & &\\ % & Parallel Session & &\\ \hline % & \multicolumn{3}{r}{\footnotesize {\it www-h1.desy.de/h1/www/publications/conf/conf\_list.html}} \\[.2em] % \end{tabular} % \end{small} % {\it H1 Preliminary results for 2006 spring conferences.} %\end{center} % \noindent % Date: \\ % Version: \\ % Editors: \\ % Referees: \\ % Comments by %\begin{flushright} %H1prelim-04-063\\ %July 28, 2004 %\end{flushright} \begin{center} %{\it {\large version 1.08 of \today}} \\[.3em] \begin{small} \begin{tabular}{llrr} %Submitted to & \multicolumn{3}{r}{\footnotesize Electronic Access: {\it http://www-h1.desy.de/h1/www/publications/conf/conf\_list.html}} \\[.2em] \hline %Submitted to & \multicolumn{3}{r}{\footnotesize {\it www-h1.desy.de/h1/www/publications/conf/conf\_list.html}} \\[.2em] \hline Submitted to & & & %\epsfig{file=/h1/www/images/H1logo_bw_small.epsi,width=2.cm} \\[.2em] \hline \epsfig{file=H1logo_bw_small.epsi,width=2.cm} \\[.2em] \hline \multicolumn{4}{l}{{\bf XV International Workshop on Deep-Inelastic Scattering and Related Subjects,}}\\ \multicolumn{4}{l}{{ DIS 2007 April~16-20,~2007,~Munich}} \\ % & Abstract: & &\\ % & Parallel Session: & &\\ \hline & \multicolumn{3}{r}{\footnotesize {\it www-h1.desy.de/h1/www/publications/conf/conf\_list.html}} \\[.2em] \end{tabular} \end{small} \end{center} \vspace{2cm} \begin{center} \begin{Large} %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% {\bf \boldmath A Search for Excited Neutrinos in $e^{-}p$~ collisions at HERA} %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \vspace{2cm} H1 Collaboration \end{Large} \end{center} \vspace{1cm} \begin{abstract} \noindent We present a search for excited neutrinos using all $e^{-}p$~data collected by the H1 experiment at HERA at center-of-mass energy of $318$ GeV with an integrated luminosity of $184$~pb$^{-1}$. The electroweak decay of excited neutrinos, ${\nu}^{*}\rightarrow{\nu}{\gamma}$, ${\nu}^{*}\rightarrow{\nu}Z$, ${\nu}^{*}{\rightarrow}eW$ are considered and possible final states resulting from the $Z$ or $W$ leptonic and hadronic decays are taken into account. No evidence for excited neutrino production is found. Mass dependent exclusion limits are determined for the ratio of the coupling to the compositeness scale, $f/{\Lambda}$. These limits extend the excluded region to higher masses than has been possible in previous searches. \end{abstract} \vspace{1.5cm} \end{titlepage} \newpage \pagestyle{plain} %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \section{Introduction} %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% The discovery of excited states of quarks or leptons as predicted by compositness models~\cite{Harari:1982xy,Boudjema:1992em} would provide a convincing evidence for a new substructure of matter. Electron-proton interactions at very high energies provide ideal conditions to look for excited states of first generation fermions. In particular a magnetic type coupling of the electron would allow for the production of single excited neutrinos ($\nu^*$) trough t-channel W boson exchange. %The phenomenology of this process is described in~\cite{Hagiwara:1985wt,Baur:1989kv,Adloff:2000gv} In this paper we present a search for excited neutrinos using all $e^{-}p$ HERA collider data of the H1 experiment. The data collected at electron and proton beam energies of $27.6$ GeV and $920$ GeV respectively corresponds to an integrated luminosity of $184$ pb$^{-1}$. The excited neutrinos are searched for through all their electroweak decays into a fermion and a gauge boson ($\gamma$, $W$ and $Z$). Hadronic decays as well as main leptonic decay channels of the $W$ and $Z$ bosons are considered. % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % \section{Introduction} % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % Models of composite leptons and quarks ~\cite{Harrari:1979} were introduced in an attempt to provide an explanation for the family structure of the known fermions and for their pattern of masses. A natural consequence of these models is the existence of excited states of leptons and quarks. It is often assumed that the compositeness scale might be in the TeV region, which would give excited fermion masses in the same energy domain. However, the dynamics at the constituent level being unknown, the lowest % % In this paper a search for excited neutrinos is presented using $e^{-}p$ HERA collider data of the H1 experiment. The data collected in 2005 at electron and proton beam energies of 27.5 GeV and 920 GeV respectively corresponds to an integrated luminosity of 114 pb$^{-1}$. The excited neutrinos are searched for through all their electroweak decays into a fermion and a gauge boson. Only the subsequent hadronic decays of the W and Z gauge boson are considered. % % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \section{Phenomenology} %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Compositeness models~\cite{Harari:1982xy,Boudjema:1992em,Hagiwara:1985wt,Baur:1989kv} attempt to explain the hierarchy of masses in the Standard Model by the existence of a substructure within the fermions. Several of these models predict excited states of the known leptons. Excited leptons are assumed to have the same electroweak SU(2) and U(1) gauge couplings, $g$ and $g'$, to the vector bosons, but are expected to be grouped into both left- and right-handed weak isodoublets with vector couplings. The existence of the right-handed doublets is required. In $ep$ collisions, excited leptons could be produced via the process $ep{\rightarrow}F^{*}X$ (here X represents the proton remnant or proton in the case of elastic $e^*$ production), as a result of the F*FV couplings. Depending on the details of these couplings, excited leptons could be detected in the photonic, charged current, or neutral current channels. The branching ratio of the excited leptons into the different vector bosons are determined by the strength of the three F*FV couplings. We use the effective Lagrangian: \be L_{F^{*}F} = \frac{1}{2\Lambda}{\bar{F^{*}_{R}}}{{\sigma}^{\mu\nu}}[gf\frac{\vec{\tau}}{2}{\partial}_{\mu}{\vec{W_{\nu}}}+g'f'\frac{Y}{2}{\partial}_{\mu}B_{\nu}]{F_{L}} + h.c. \ee which describes the generalised magnetic de-excitation of the excited states. The matrix ${{\sigma}^{\mu\nu}}$ is the covariant bilinear tensor, $\tau$ are the Pauli matrices, $W_{{\mu}{\nu}}$ and $B_{{\mu}{\nu}}$ represent the fully gauge invariant field tensors, and Y is the weak hypercharge. The parameter $\Lambda$ has units of energy and can be regarded as the compositeness scale, while $f$ and $f'$ are the weight associated with the different gauge groups. The relative values of $f$ and $f'$ also affect the size of the single-production cross-sections and their detection efficiencies. Depending on their relative values, either the photonic decay, the CC decay, or the NC decay will have the largest branching ratio, depending on the respective couplings: $$ f_{\gamma} = e_{f}f' + I_{3L}(f-f') , f_{W} = \frac{f}{{\sqrt{2}}s_{\omega}} , f_{Z} = \frac{4I_{3L}(c_{\omega}^{2}f+s_{\omega}^{2}f')-4e_{f}s_{\omega}^{2}f'}{4s_{\omega}c_{\omega}} $$ where $e_{f}$ is the excited fermion charge, $I_{3L}$ is the weak isospin, and $s_{\omega}(c_{\omega})$ are the sine (cosine) of the Weinberg angle ${\theta}_{\omega}$. Our results for excited neutrinos will be interpreted using the two complementary coupling assignments, $f = f'$ and $f = -f'$. The first uses $f = f'$, so that the photonic decay of the ${\nu}^{*}$ is forbidden, the second uses $f=-f'$, so that all ${\nu}^*$ decays into $\nu\gamma$, $\nu{Z}$ and $eW$ are allowed. % % In addition to the results for the two assignments f=f' and f=-f', a new method is introduced which gives limits in excited neutrinos independent of the relative values of f and f'. % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % \section{The physical setup} % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % It is convenient to choose a specific phenomenological model to quantify the experimental sensitivity which, for a narrow resonance, depends only on its mass and decay angular distribution. The most commonly used model~\cite{Baur:1990,Hagiwara:1985} is based on the assumptions that the excited fermions have spin and isospin 1/2 and both left-handed, $F^{*}_{L}$ and right-handed components, $F^{*}_{R}$ are in weak isodoublets. The Lagrangian describles the transitions between known fermions, $F^{*}_{L}$, % $$ % L_{F^{*}F} = \frac{1}{\Lambda}{\bar{F^{*}_{R}}}{{\sigma}^{\mu\nu}}[gf\frac{\vec{\tau}}{2}{\partial}_{\mu}{\vec{W_{\nu}}}+g'f'\frac{Y}{2}{\partial}_{\mu}B_{\nu}+g_{s}f_{s}\frac{\lambda^{a}}{2}{\partial}^{\mu\nu}{G^{a}_{\nu}}]{F_{L}} + h.c % $$ % where $\Lambda$ is the compositeness scale: $\vec{W_{\nu}}$, $B_{\nu}$, $G^{a}_{\nu}$ are the SU(2), U(1) and SU(3) fields: $\vec{\tau}$, $Y$, ${\Gamma}^{a}$ are the corresponding gauge-group generators; and $g$, $g'$, $g_{s}$ are the coupling constants. The free parameters $f$, $f'$ and $f_{s}$ are weight factord associated with the three gauge groups and depend on thr specific dynamics describing the cpmpositeness. For an excited fermion decays to be observable, $\Lambda$ must be finite and at least o % % For excited electrons, the conventional relation $f = f'$ is adopted. The dominant contribution to $e^{*}$ production is t-channel $\gamma$ exchange, in which roughly 50\% of the excited electrons would be produced elastically. % % For excited quarkd, $f = f'$ is also adopted. There are stringent limits on $f_{s}$ in $q^{*}$ production from the Tevatron~\cite{Abe:1997}. % % Since excited neutrinos production requires W exchange, the cross section for $M_{{\nu}^{*}} > 200$~GeV in $e^{-}p$ collisions is two orders of magnitude higher than in $e^{+}p$. Therefore, $e^{-}p$ reactions offer much greater sensitivity for the ${\nu}^{*}$ search than $e^{+}p$ reactions. In this paper, we choose to concentrate ont he excited neutrinos in $e^{-}p$ collisions and two very different assumtion are contrasted: the first uses $f = f'$, so that the photonic decay of the ${\nu}^{*}$ is forbi %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \section{Standard Model processes and their simulation} %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Final states of events selection in this analysis contain either missing transverse momentum or an high energy electron (or photon) and a photon or jets with high tranverse energy. The main backgrounds from Standard Model (SM) processes which could mimic such signatures are mostly neutral current (NC) and charged current (CC) deep-inelastic scattering (DIS) or photoproduction processes. The Born, QCD Compton and Boson Gluon Fusion matrix elements are used in the RAPGAP~\cite{Jung:1993gf} event generator to model NC DIS and CC DIS events. The QED radiative effects arising from real photon emission from both the incoming and outgoing electrons are simulated using the HERACLES~\cite{Kwiatkowski:1990es} generator. To simulate the direct and resolved photoproduction of jets, prompt photon production and the resolved photoproduction of photon pairs, the PYTHIA $6.1$ event generator~\cite{Sjostrand:2000wi} is used. Light and heavy flavoured jets are generated. The simulation contains the Born level hard scattering matrix elements and radiative QED corrections. Processes with the production of three or more jets are accounted for using leading logarithmic parton showers as a representation of higher order QCD radiation. Hadronisation is modelled using Lund string fragmentation~\cite{Sjostrand:2000wi}. The prediction of processes with two or more high transverse momentum jets is scaled by a factor of $1.2$ to normalise the leading order Monte Carlos to next-to-leading order QCD calculations~\cite{Adloff:2002au}. Contributions from elastic and quasi-elastic QED-Compton scattering are simulated with the WABGEN~\cite{Berger:kp} generator. Possible contributions arising from the production of $W$ bosons or multi-lepton events are also considered and modelled using the EPVEC~\cite{Baur:1991pp} and GRAPE~\cite{Abe:2000cv} event generators, respectively. % % Monte Carlo simulations of excited neutrino production and decay are necessary to evaluate acceptance losses due to selection requirements. The excited neutrino analyses are based on the phenomenology described in section 2. The excited neutrino (${\nu}^{*}$) simulations is performed by the H1NuStar generator which we have just developped. This generator doesn't uses the narrow width approximation (NWA) for the calculation of the production cross section. It takes into account the natural width for the % %The narrow-width approximation is not assumed. All generated events are passed through the full GEANT~\cite{Brun:1987ma} based simulation of the H1 apparatus, which takes into account the running conditions of the different data taking periods. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \section{The H1 Detector} %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% A detailed description of the H1 experiment can be found in \cite{Abt:h1}. Only the H1 detector components relevant to the present analysis are briefly described here. Jets and electrons are measured with the Liquid Argon (LAr) calorimeter~\cite{Andrieu:1993kh}, which covers the polar angle\footnote{ The origin of the H1 coordinate system is the nominal $ep$ interaction point, with the direction of the proton beam defining the positive $z$-axis (forward region). The transverse momenta are measured in the $xy$ plane. The pseudorapidity $\eta$ is related to the polar angle $\theta$ by $\eta = -\ln \, \tan (\theta/2)$.} range $4^\circ < \theta < 154^\circ$ with full azimuthal acceptance. Electromagnetic shower energies are measured with a precision of $\sigma (E)/E = 12\%/ \sqrt{E/\mbox{GeV}} \oplus 1\%$ and hadronic energies with $\sigma (E)/E = 50\%/\sqrt{E/\mbox{GeV}} \oplus 2\%$, as measured in test beams. In the backward region, energy measurements are provided by a lead/scintillating-fiber (SpaCal) calorimeter~\cite{Appuhn:1996na} covering the range $155^\circ < \theta < 178^\circ$. The central and forward tracking detectors are used to measure charged particle trajectories, to reconstruct the interaction vertex and to supplement the measurement of the hadronic energy. The LAr and inner tracking detectors are enclosed in a super-conducting magnetic coil with a strength of $1.15$~T. % The return yoke of the coil is the outermost part of the detector and is % equipped with streamer tubes forming the central muon detector % ($4^\circ < \theta < 171^\circ$). % In the forward region of the detector ($3^\circ < \theta < 17^\circ$) a set of % drift chamber layers (the forward muon system) detects muons and, together with an % iron toroidal magnet, allows a momentum measurement. The luminosity measurement is based on the Bethe-Heitler process $ep \rightarrow ep \gamma$, where the photon is detected in a calorimeter located downstream of the interaction point. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \section{Data Analysis} %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Events are first selected by requiring that the event vertex be reconstructed within $35$ cm in $z$ of the nominal interaction point. In addition topological filters and timing vetoes are applied to remove background events induced by cosmic showers and other non-$ep$ sources. The main trigger of the events is provided by the LAr calorimeter. The trigger efficiency is close to $100\%$ for events having an electromagnetic deposit in the LAr (electron or photon) with an energy greater than $10$~GeV~\cite{Adloff:2003uh}. For events with missing transverse momentum above $20$ GeV, the trigger efficiency is $\sim$ $90$~\%. The identification of electrons or photons is first based on the measurement of a compact and isolated electromagnetic shower in the LAr calorimeter. In addition, the electromagnetic cluster is required to be be isolated from jets by a distance $R > 0.5$ to the jet axis in pseudorapidity-azimuth. Energy deposits in the calorimeter and tracks in the inner tracking system are used to form combined cluster-track objects, from which the hadronic energy is reconstructed. Jets are defined using an inclusive $k_T$ algorithm \cite{Ellis:1993tq,Catani:1993hr} with a minimum transverse momentum of $3$ GeV. The missing transverse momentum $P_T^{miss}$ of the event is derived from all identified particles and energy deposits in the event. \subsection{$\nu\gamma$ Resonance Search} For this search, the principal signature is an isolated electromagnetic cluster in events with missing tranverse momentum. Backgrounds arise from CC DIS events with isolated ${\pi}^0$ or initial or final state radiation. The presence of a neutrino is inferred by requiring $P_{T}^{miss} > 15$~GeV. A photon is tagged by identifying an electromagnetic cluster with $P_T^\gamma >$ $20$ GeV in a polar angle range $5^{\circ} < {\theta}^{\gamma} < 120^{\circ}$. No well measured track should point to the electromagnetic cluster within a distance of closest approach (DCA) of $12$ cm. If $P_{T}^{miss} < 30$~GeV, thigther vetoes are applied on any charged track pointing to the electromagnetic cluster: no track should be present with a DCA to the cluster below $24$ cm or within $R <0.5$ in pseudorapidity-azimuth. Radiative CC DIS events are suppressed by requiring that the four-momentum transfer squared determined from the electromagnetic cluster be $\log Q^2_\gamma > 3.5$ GeV$^2$. We also demand that the transverse momentum of the photon be larger that $40$~GeV for events with the variable $\sum_i E^i - P^i_z$ lower than $45$~GeV, where the sum runs over all visible particles. The final state for the signal contains in most of the cases a recoil jet, due to the ${\nu}^{*}$ production through a $t$-channel $W$ boson exchange. Hence in the final selection the presence of at least one jet with $P_{T}^{jet} > 5$~GeV is also imposed. Nine event survives the selection criteria. The expected SM contribution is $15$~$\pm$~$4$ events and is dominated by CC DIS events. The resulting selection efficiency varies from $55$\% to $40$\% for excited neutrinos of mass $150$ GeV and $250$ GeV, respectively. \subsection{$\nu{q}{\bar{q}}$ Resonance Search} % % For this search, the dominant SM background consists of multi-jet CC DIS events with a moderate contribution from photoproduction. % The presence of a neutrino is inferred from substantial missing momentum ($P_{T}^{miss} > 12$~GeV). % We use a subsample of events with at least two jets, each having a high transverse momentum larger than 20 and 15 GeV, respectively, and a polar angle between $5^{\circ}$ and $130^{\circ}$. % The hadron system must exhibit a large transverse momentum ($P_{T}^{h} > 20$~GeV) and a polar angle larger than $20^{\circ}$ in order to remove photoproduction events. For this search, the dominant SM background consists of multi-jet CC DIS events with a moderate contribution from photoproduction. The presence of a neutrino is inferred from substantial missing momentum $P_{T}^{miss} > 20$~GeV. We use a subsample of events with at least two jets, each having a transverse momentum larger than $20$ and $15$ GeV, respectively, and a polar angle between $5^{\circ}$ and $130^{\circ}$. Moreover, the hadron system must exhibit a large polar angle, $\gamma_h > 20^{\circ}$, in order to remove photoproduction events. At low $P_{T}^{miss}$, cuts on the variable $\sum_i E^i - P^i_z$ and on the ratio $V_{ap}/V_{p}$ of transverse energy flow anti-parallel and parallel to the hadronic final state~\cite{Adloff:2003uh} are used to suppress CC DIS events. In events with $P_{T}^{miss} <$ $30$ GeV, we require $V_{ap}/V_{p} > $ $0.1$ and in addition if $P_{T}^{miss} <$ $50$ GeV events with $\sum_i E^i - P^i_z < $ $25$ GeV are removed. Finally, to further suppress the background from CC DIS a cut on the jet multiplicity ($n_{jets}{\geq}3$) is applied in the region of lower missing transverse momentum ($P_{T}^{miss} < 50$~GeV). The $Z$ candidate is reconstructed from the combinaison of two jets with an invariant mass closest to the nominal $Z$ boson mass. The reconstructed mass is required to be above $60$ GeV. After these cuts, $111$ events are found compared to an expected SM contribution of $102$~$\pm$~$24$ events. No significant excess is observed. The acceptance for $\nu^*$ events in this final state is approximately $40$~\% for $M_{\nu^*} > $ $150$ GeV. \subsection{e$q{\bar{q}}$ Resonance Search} In this channel multi-jet NC DIS events constitute the main contribution from SM processes. Events are selected by the presence of an electron in the LAr ($5^\circ< \theta^e < 90^\circ$) with $Q^2_e > 2500$~GeV$^2$ or a tranverse momentum $P_T^e$ greater than 25 GeV. The restriction on the electron polar angle to the forward region of the LAr removes a large part of the NC DIS contribution. The presence of at least two high $P_T$ jets with $P_{T}^{jet1,\; jet2} > 20, 15$~GeV and $5^{\circ} < \theta^{jet1,\; jet2} < 130^{\circ}$ is required. Then, a $W$ candidate is reconstructed in those events from the combinaison of two jets with an invariant mass closest to the nominal $W$ boson mass. The reconstructed mass of the $W$ candidate is required to be larger than $40$ GeV. To increase the separation power between NC DIS events and a $\nu^*$ signal we demand that the polar angle of the higest $P_T$ jet associated to the $W$ candidate be lower than $80^\circ$ and that the events with $P_T^e <$ $65$ GeV contain at least three jets. After the selection, $198$ events are observed while $189$ $\pm$ $33$ are expected from the SM. The efficiency for selecting $\nu^*$ events varies between $30$--$40$~\% in this decay channel. % \subsection{Systematic uncertainties} % % The most important sources of systematic uncertainty were: % % \begin{description} % \item[$\bullet$] The energy scale of the calorimeter was varied from 0.7\% to 3\% for electron and by 2\% for hadrons. % % \item[$\bullet$] The polar angle was of 3 mrad for electron, 10 mrad for jets center and 5 mrad for jets forward. % % \item[$\bullet$] The uncertainty on the photon identification was of 5\%. % % \item[$\bullet$] The uncertainty on the $V_{ap}/V_{p}$ variable cut amount to 10\%. % % \item[$\bullet$] The uncertainty on the trigger efficiency was estimated to 3\%. % % \item[$\bullet$] The uncertainty on the processes like $gP$, NC and CC requiring at least 2 jets in events and W production was varied of 15\%, 15\%, 15\% respectively. % % \item[$\bullet$] Finally, the luminosity measurement leads to a normalization uncertainty of 2.5\%. % % \end{description} % \subsection{Resonance Search in leptonic decays of $W$ and $Z$ bosons} In the search for ${\nu}^{*} {\rightarrow} {e}{W_{{\hookrightarrow}\nu\mu}}$ events with a $P_T^{miss} > 12$ GeV and one isolated electron and muon are selected. The electron and muon have to be isolated and to verify $P_T^{e,\mu} > 20, 10$ GeV and $\theta_{e,\mu} < 100^\circ, 160^\circ$. After this selection no data event is left while $0.54 \pm 0.04$ SM background events are expected. The signature for the ${\nu}^{*} {\rightarrow} {e}{W_{{\hookrightarrow}\nu e}}$ and ${\nu}^{*} {\rightarrow} {\nu}{Z_{{\hookrightarrow}ee}}$ channels is similar and consist of two high $P_T$ electrons and a large missing transverse momentum, $P_T^{miss} > 20$ GeV. Two isolated electromagnetic clusters are first required, with a transverse momentum larger than $20$ and $15$ GeV and a polar angle $5^\circ < \theta_{e1,e2} < 100^\circ, 120^\circ$, respectively. To reduce background from Compton events, a track of any quality has to be associated to each electromagnetic cluster in the central region ($\theta_e >35^\circ$). Events from the ${W_{{\hookrightarrow}\nu e}}$ decay channel are selected by imposing the invariant mass of the $\nu$ and the electromagnetic cluster to be compatible with the $W$ boson mass within $20$ GeV. Events in which the invariant mass of the two electromagnetic clusters is close to the mass of the $Z$ boson by $10$ GeV are attributed to the ${Z_{{\hookrightarrow}ee}}$ decay channel. No candidate is found in both channels, compared to SM expectations of $0.6 \pm 0.3$ and $0.12 \pm 0.04$ in the $W$ and $Z$ decay channels, respectively. \section{Interpretation} The event yields observed in each decay channel are summarised in table~\ref{tab:nustaryields}. The observed event yields are in good agreement with SM expectations, which are dominated by NC DIS for $e{q}{\bar{q}}$ resonance search and by CC DIS events for $\nu\gamma$ and $\nu{q}{\bar{q}}$ resonance searches. The distributions of the invariant mass of the data events and of expected SM background are compared in figure~\ref{fig:Mass} for the main three channels. Both data and SM are in agreement and no additional resonance is seen in the data. No data events is observed in channels corresponding to leptonic decays of $W$ or $Z$ bosons in agreement with SM expectations below one in those classes. Since there is no evidence for excited neutrinos, upper limits on the coupling $f/{\Lambda}$ as a function of the mass of the excited neutrino are derived. Limits are presented at the 95~\% confidence level and are obtained using a modified frequentist approach \cite{Junk:1999kv} which takes statistical and systematical uncertainties into account. The resulting limits after combination of all decay channels are presented in figure~\ref{fig:LimitCoupling}, for the conventional assumptions $f = - f'$ and $f = + f'$. Note that the decay $\nu^* \rightarrow \nu \gamma$ is forbidden for $f = + f'$. This new result improve significantly the bounds previously obtained by H1~\cite{Adloff:2001me} using 15~pb$^{-1}$ of HERA I data and extend up to the HERA kinematical limit. Considering the assumption $f/\Lambda = 1/M_{\nu^*}$ excited neutrinos with masses up to 211 GeV (195 GeV) are excluded for $f = - f'$ ($f = + f'$). For comparisons, results obtained in $e^+ e^-$ collisions at LEP by the L3 collaboration~\cite{Acciarri:2000} are also shown on figure~\ref{fig:LimitCoupling}. The limits from the present analysis are more stringent at high masses and extend beyond the kinematic reach of previous searches. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \section{Summary} %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% In summary, using all $e^{-}p$ data collected by the H1 experiment with an integrated luminosity of 184~pb$^{-1}$ a search for the production of excited neutrinos has been performed. The excited neutrino decay channels ${\nu}^{*} {\rightarrow} {\nu}{\gamma}$, ${\nu}^{*} {\rightarrow} {\nu}{Z}$ and ${\nu}^{*} {\rightarrow} {e}{W}$ with subsequent hadronic or leptonic decays of the $W$ and $Z$ bosons have been considered and no indication of a signal was found. New limits on the coupling $f/\Lambda$ as a function of the excited neutrino masses have been established, using the two specific relations between the couplings $f = f'$ and $f = - f'$. Assuming $f = - f'$ and $f/\Lambda=1/M_{\nu^*}$ excited neutrinos with a mass lower than 211 GeV are excluded at 95\% confidence level. The present results greatly extend previous searched domains at HERA and confirm the HERA unique sensitivity for excited neutrinos with masses beyond the LEP reach. % In this section the description of the selection criteria for the various decay channels is organized according to the experimental signatures of the final states. % % In common for all analyses, background is rejected by requiring that there is a primary vertex within ${\pm}$~35~cm of the nominal vertex value, and that the event time, measured with the center tracking chamber, coincides with that of bunch crossing. In addition topological filters against cosmic and halo muons are used. A small number of cosmic and halo muons finnaly are removed by a visual scan. % % The identification of electrons or photons, performed in the LAr calorimeter, first relies on calorimetric information by exploiting the shape of the energy density expected from the deveplopment of an electromagetic shower to define electromagnetic clusters. An electron is identified as an electromagnetic cluster with a track linked to it. A photon in contrast should have no track pointing to it within a distance of 24~cm. In this analysis, an electron or a photon candidates are require to be isolated % % The selection criteria adapted to the different event topologies are described below: % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % \section{Mass reconstruction of excited fermions} % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % To improved the mass resolusion, the kinematic constraints could be applied: in all decays involving a final-state W or Z, the mass of their decay products was constrained to be the mass of the respective boson. % % \begin{description} % \item[$\bullet$] For {${\nu}^{*} {\rightarrow} {\nu}{\gamma}$} : the mass of excited neutrino was determined from the invariant mass of the photon and the neutrino. The four-momentum of the neutrino was obtained using energy-momentum conservation. % \item[$\bullet$] For {${\nu}^{*} {\rightarrow} {\nu}Z_{{\hookrightarrow}qq}$} : the invariant mass is calculated for an event by combining the four-momentum of the neutrino above and the two jets attributed to the decay of the Z boson. % \item[$\bullet$] For {${\nu}^{*} {\rightarrow} eW_{{\hookrightarrow}qq}$} : the invariant mass is calculated for an event by combining the four-momenta reconstructed from the electromagnetic cluster and the two jets attributed to the decay of the W boson. % \end{description} % % The Gaussian mass resolutions in each decay channel are shown as a function of $\nu*$ mass in figure~\ref{fig:Resolution}. The resolutions for the $\nu\gamma$, $eW$ channels are better than for the $\nu{Z}$. The mass resolution for the $\nu\gamma$ channel is up to 5 GeV, for the $eW$ is between 2 GeV and 15 GeV and for the $\nu{Z}$ channel is from 14 GeV to 19 GeV. % % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % \section{Results} % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % The event yields observed for each channel are summazied in table~\ref{tab:nustaryields}. In three decay channels, the observed event yields are in good agreement with SM expectations, which are dominated by neutral current DIS for $e{q}{\bar{q}}$ resonance search and are dominated by charged current DIS for $\nu\gamma$, $\nu{q}{\bar{q}}$ resonance search. The excited neutrinos selection efficiency in each decay channel are shown in figure~\ref{fig:Efficiency}. % % % The event yields observed for each channel are summazied in table~\ref{tab:nustaryields}. The excited neutrinos selection efficiency in each decay channel are shown in figure~\ref{fig:Efficiency}. In three decay channels, the observed event yields are in good agreement with SM expectations. No significant excess of events is observed. % % The distributions of the invariant mass are compared in figure~\ref{fig:Mass} with the expected backgrounds for the ${\nu}^{*}$. No evidence for a resonance is seen. The events display corresponding with the high $M_{\nu\gamma}$, $M_{\nu{Z}}$, $M_{eW}$ invariant mass are shown in figure~\ref{}. % % The search for the Z/W bosons in the leptonic decay channel are implemented. The agreement with the SM prediction is good but we also observed no evidence for resonance in these cases. % Since there is no evidence for excited neutrinos, upper limits at 95\% confidence level on cross-section and $f/{\Lambda}$ were derived. Upper limits has been calculated using T.Junk's code (Tlimit Root implementation) and sliding window method. In which, the systematics uncertainty on limit computations are taken into account. % % \subsection{Upper Limits on Cross-Sections} % % The limits on the cross-section and decay branching fraction are determined at a Confidence Level (CL) of 95\% as a function of the excited neutrinos mass. A mass window is shifted over the whole mass range in steps of 2 GeV. The width of each window is chosen according to the resolution for the corresponding mass. The number of observed and expected events is counted within a sliding mass window which is adopted to the width of the expected excited neutrino signal. Statistic and systematic errors are t % % The expected and observed limits on the product of the ${\nu}^{*}$ production cross-section and the decay branching fraction with the assumptions $f = -f'$ and $f = +f'$ are shown in figure~\ref{fig:LimitCrosssection} . % % \subsection{Upper Limits on Coupling Parameters} % % Assuming fixed numerical relations between $f$ and $f'$, the cross-section depends only on $f/{\Lambda}$ and $M_{{\nu}^{*}}$, and thus constraints on $f/{\Lambda}$ can be derived. Conventional assumptions are $f = -f $ or $f = +f'$. From the coupling constant relations it can be seen that the coupling of the ${\nu}^{*}$ to the $\nu\gamma$ decay channel is proportional to $(f-f')$. % % % In figure~\ref{fig:LimitCrosssection}, the expected and observed limits on the ration $f/{\Lambda}$ are given the ${\nu}^{*}$, assumption $f = -f'$ and $f = +f'$. % The H1 expected and observed limits on the ratio $f/{\Lambda}$ for each decay channel and after combination of all decay channels are given as a function of the $\nu*$ mass in figure~\ref{fig:LimitCoupling}, assumption $f = -f'$ and $f = +f'$. In particular when $f = +f'$ the ${\nu}^{*} {\rightarrow} {\nu}{\gamma}$ is forbidden. For the $f = -f'$ case, the values of the limits for $f/{\Lambda}$ vary between 2~$\times$~10$^{-2}$ and 10$^{-3}$ for an $\nu*$ mass ranging from 100 GeV to 260 GeV. The values % % % Figure~\ref{fig:LimitCrosssection} also shows for comparation results obtained by using 98/99 cuts selection in this analysis~\cite{Nico:2003}. Our limits are more stringent than 98/99 cuts selection. % % Figure~\ref{fig:LimitCoparison} shows for comparison results obtained by using H1 $e^{-}p$ data at HERA I with an integrated luminosity of 15 pb$^{-1}$ and by the L3 collaboration on $e^{+}e^{-}$ collisions at center of mass energies up to 202 GeV at LEP II~\cite{Acciarri:2000}. The H1 limits are more stringent at high masses beyond the kinematic reach of LEP II. % According to the results obtained by the addition of the Z/W leptonic decay channels, the exclusion limits are improved by combining with the Z/W in leptonic decay channels. Figure~\ref{fig:Leptonic} shows the comparison between combined limits. % More generally, limits on $f/{\Lambda}$ as a function of $f'/f$ are shown in figure~\ref{} for three $\nu*$ masses (). It is worth noting that excited neutrinos have vanishing the electromagnetic for $f = +f'$. In this case the $\nu*$ is produced through pure W/Z bosons exchange. For the high $\nu*$ masses and some values of the couplings, no limits are given because the natural width of the $\nu*$ would become extremely large. % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % \section{Limits on Excited Neutrinos Production} % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % No evidence was seen for excited neutrinos in any of the channels. Therefore, upper limits on the product of the ${\nu}^{*}$ production cross-section and the decay branching and upper limits on the coupling parameters have been derived. Upper limits has been calculated using T.Junk's code (Tlimit Root implementation) and sliding window method. % % \subsection{Upper Limits on Cross-Sections} % % The limits on the cross-section and decay branching fraction are determined at a Confidence Level (CL) of 95\% as a function of the excited neutrinos mass. A mass window is shifted over the whole mass range in steps of 2 GeV. The width of each window is chosen according to the resolution for the corresponding mass. The number of observed and expected events is counted within a sliding mass window which is adopted to the width of the expected excited neutrino signal. Statistic and systematic errors are t % % The expected and observed limits on the product of the ${\nu}^{*}$ production cross-section and the decay branching fraction with the assumptions $f = -f'$ and $f = +f'$ are shown in figure 3. % % \subsection{Upper Limits on Coupling Parameters} % % Assuming fixed numerical relations between $f$ and $f'$, the cross-section depends only on $f/{\Lambda}$ and $M_{{\nu}^{*}}$, and thus constraints on $f/{\Lambda}$ can be derived. Conventional assumptions are $f = -f $ or $f = +f'$. From the coupling constant relations it can be seen that the coupling of the ${\nu}^{*}$ to the $\nu\gamma$ decay channel is proportional to $(f-f')$. % % % In figure~\ref{fig:LimitCrosssection}, the expected and observed limits on the ration $f/{\Lambda}$ are given the ${\nu}^{*}$, assumption $f = -f'$ and $f = +f'$. % The H1 expected and observed limits on the ratio $f/{\Lambda}$ for each decay channel and after combination of all decay channels are given as a function of the $\nu*$ mass in figure~\ref{fig:LimitCrosssection}, assumption $f = -f'$ and $f = +f'$. In particular when $f = +f'$ the ${\nu}^{*} {\rightarrow} {\nu}{\gamma}$ is forbidden. For the $f = -f'$ case, the values of the limits for $f/{\Lambda}$ vary between 2~$\times$~10$^{-2}$ and 10$^{-3}$ for an $\nu*$ mass ranging from 100 GeV to 260 GeV. The va % % % Figure~\ref{fig:LimitCrosssection} also shows for comparation results obtained by using 98/99 cuts selection in this analysis~\cite{Nico:2003}. Our limits are more stringent than 98/99 cuts selection. % % Figure~\ref{fig:LimitCoparison} shows for comparison results obtained by the ZEUS collaboration in $e^{-}p$ collisons at center of mass energies up to 318 GeV at HERA and by the L3 collaboration on $e^{+}e^{-}$ collisions at center of mass energies up to 202 GeV at LEP II~\cite{Acciarri:2000}. The H1 limits are more stringent at high masses beyond the kinematic reach of LEP II. % % More generally, limits on $f/{\Lambda}$ as a function of $f'/f$ are shown in figure~\ref{} for three $\nu*$ masses (). It is worth noting that excited neutrinos have vanishing the electromagnetic for $f = +f'$. In this case the $\nu*$ is produced through pure W/Z bosons exchange. For the high $\nu*$ masses and some values of the couplings, no limits are given because the natural width of the $\nu*$ would become extremely large. % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % \section{Summary} % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % In summary, using $e^{-}p$ data collected in 2005 with an integrated luminosity of 114~pb$^{-1}$~a search for the production of excited neutrionos has been performed. The event yields in $\nu\gamma$, $\nu{Z}$, and $eW$ are in good agreement with the SM predictions. No indication of a signal was found. % % New limits have been established as function of couplings and excited neutrinos masses both for specific relations between the couplings ($f = -f'$ and $f = +f'$) and independent of the ratio of $f$ and $f'$. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \newpage %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \begin{thebibliography}{99} %%%%%%%%%%%%%%% excited fermion pheno %%%%%%%%%%%%%%%%%%%%% % \bibitem{Harrari:1979} % S.~Weinberg,Phys.\ Rev. {\bf D 20} (1976); ibid Phys.\ Rev. {\bf D 19} (1979) 1277 % H.~Harrari, Phys.\ Lett. {\bf B 98} (1981) 269. % \bibitem{Derrick:1995} % ZEUS Collaboration, M.~Derrick {\it et al.}, Z.\ Phys.\ J.~{\bf C 65} (1995) 627. %\cite{Harari:1982xy} \bibitem{Harari:1982xy} H.~Harari, %``Composite Models For Quarks And Leptons,'' Phys.\ Rept.\ {\bf 104} (1984) 159. %%CITATION = PRPLC,104,159;%% %\cite{Boudjema:1992em} \bibitem{Boudjema:1992em} F.~Boudjema, A.~Djouadi and J.~L.~Kneur, 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%%CITATION = CPHCB,86,147;%% %\cite{Sjostrand:2000wi} \bibitem{Sjostrand:2000wi} T.~Sjostrand, P.~Eden, C.~Friberg, L.~Lonnblad, G.~Miu, S.~Mrenna and E.~Norrbin, %``High-energy-physics event generation with PYTHIA 6.1,'' Comput.\ Phys.\ Commun.\ {\bf 135} (2001) 238, [hep-ph/0010017]. %%CITATION = HEP-PH 0010017;%% %\cite{Kwiatkowski:1990es} \bibitem{Kwiatkowski:1990es} A.~Kwiatkowski, H.~Spiesberger and H.~J.~Mohring, %``Heracles: An Event Generator For E P Interactions At Hera Energies Including Radiative Processes: Version 1.0,'' Comput.\ Phys.\ Commun.\ {\bf 69} (1992) 155. %%CITATION = CPHCB,69,155;%% %\cite{Adloff:2002au} \bibitem{Adloff:2002au} C.~Adloff {\it et al.} [H1 Collaboration], %``Measurement of dijet cross sections in photoproduction at HERA,'' Eur.\ Phys.\ J.\ C {\bf 25} (2002) 13, [hep-ex/0201006]. %%CITATION = HEP-EX 0201006;%% %\cite{Berger:kp} \bibitem{Berger:kp} C.~Berger and P.~Kandel, %``A New Generator For Wide Angle Bremsstrahlung,'' %\href{http://www.slac.stanford.edu/spires/find/hep/www?irn=4270703}{SPIRES entry} Prepared for Workshop on Monte Carlo Generators for HERA Physics Hamburg, Germany, 27-30 Apr 1998. %\cite{Baur:1991pp} \bibitem{Baur:1991pp} U.~Baur, J.~A.~Vermaseren and D.~Zeppenfeld, %``Electroweak vector boson production in high-energy e p collisions,'' Nucl.\ Phys.\ B {\bf 375} (1992) 3. %%CITATION = NUPHA,B375,3;%% %\cite{Abe:2000cv} \bibitem{Abe:2000cv} T.~Abe, %``GRAPE-Dilepton (Version 1.1): A generator for dilepton production in e p collisions,'' Comput.\ Phys.\ Commun.\ {\bf 136} (2001) 126, [hep-ph/0012029]. %%CITATION = HEP-PH 0012029;%% %%%% NLO W rewaight % %\cite{Diener:2003df} % \bibitem{Diener:2003df} % K.~P.~Diener, C.~Schwanenberger and M.~Spira, % %``Photoproduction of W bosons at HERA: Reweighting method for implementing QCD corrections in Monte Carlo programs,'' % hep-ex/0302040. % %%CITATION = HEP-EX 0302040;%% %\cite{Brun:1987ma} \bibitem{Brun:1987ma} R.~Brun, F.~Bruyant, M.~Maire, A.~C.~McPherson and P.~Zanarini, %``Geant3,'' CERN-DD/EE/84-1. %%%%%%%%%%%%%%%%%%%%%%% H1 detector %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%5 \bibitem{Abt:h1} I.~Abt {\it et al.} [H1 Collaboration], %``The H1 Detector At Hera,'' %``The Tracking, calorimeter and muon detectors of the H1 experiment at HERA ,'' Nucl.\ Instrum.\ Meth.\ A {\bf 386} (1997) 310 and 348. %%CITATION = NUIMA,A386,310;%% %\cite{Andrieu:1993kh} \bibitem{Andrieu:1993kh} B.~Andrieu {\it et al.} [H1 Calorimeter Group Collaboration], %``The H1 liquid argon calorimeter system,'' Nucl.\ Instrum.\ Meth.\ A {\bf 336} (1993) 460. %%CITATION = NUIMA,A336,460;%% %\cite{Appuhn:1996na} \bibitem{Appuhn:1996na} R.~D.~Appuhn {\it et al.} [H1 SPACAL Group Collaboration], %``The H1 lead/scintillating-fibre calorimeter,'' Nucl.\ Instrum.\ Meth.\ A {\bf 386} (1997) 397. %%CITATION = NUIMA,A386,397;%% %%%%%%%%%%%%%%%% trigger efficiencies %%%%%%%%%%%%%%%%%%% %\cite{Adloff:2003uh} \bibitem{Adloff:2003uh} C.~Adloff {\it et al.} [H1 Collaboration], %``Measurement and QCD analysis of neutral and charged current cross sections %at HERA,'' Eur.\ Phys.\ J.\ C {\bf 30}, 1 (2003), [hep-ex/0304003]. %%CITATION = HEP-EX 0304003;%% %%%%%%%%%%%%%%%% kT jets %%%%%%%%%%%%%%%%%%% %\cite{Ellis:1993tq} \bibitem{Ellis:1993tq} S.~D.~Ellis and D.~E.~Soper, %``Successive combination jet algorithm for hadron collisions,'' Phys.\ Rev.\ D {\bf 48} (1993) 3160 [hep-ph/9305266]. %%CITATION = HEP-PH 9305266;%% %\cite{Catani:1993hr} \bibitem{Catani:1993hr} S.~Catani, Y.~L.~Dokshitzer, M.~H.~Seymour and B.~R.~Webber, %``Longitudinally invariant K(t) clustering algorithms for hadron-hadron collisions,'' Nucl.\ Phys.\ B {\bf 406} (1993) 187. %%CITATION = NUPHA,B406,187;%% %%%%%%%%%%%% limits %%%%%%%%%%%%%% %\cite{Junk:1999kv} \bibitem{Junk:1999kv} T.~Junk, %``Confidence level computation for combining searches with small %statistics,'' Nucl.\ Instrum.\ Meth.\ A {\bf 434} (1999) 435, [hep-ex/9902006]. %%CITATION = NUIMA,A434,435;%% %%%%%%%%%%% other nustar results %%%%%%%%%%%%%%%%% % \bibitem{Nico:2003} % N.~Delerue. {\it Recherche de leptons excit\'es dans les donn\'ees de l'exp\'erience H1 aupr\`es du collisionneur HERA}. Thesis University of M\'editerran\'ee, 2003, http://www-h1.desy.de/publications/theseslist.html %\cite{Adloff:2001me} \bibitem{Adloff:2001me} C.~Adloff {\it et al.} [H1 Collaboration], %``Search for excited neutrinos at HERA,'' Phys.\ Lett.\ B {\bf 525} (2002) 9, [hep-ex/0110037]. %%CITATION = HEP-EX 0110037;%% \bibitem{Acciarri:2000} M.~Acciarri {\it et al.} [L3 Collaboration], Phys.\ Lett.~{\bf B 502} (2001) 37, [hep-ex/0011068]. \end{thebibliography} %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \newpage % \begin{table}[] % \begin{center} % \begin{tabular}{|c||c|c||c|c|c|} % \multicolumn{5}{c}{H1 Preliminary 114 pb$^{-1}$ (2005)}\\ % \hline % Selection & Data & SM & CC-DIS & NC-DIS & ${\gamma}p$ \\ % % \hline % ${\nu}^{*} {\rightarrow} {e}{W_{{\hookrightarrow}qq}}$ & $136$ & $118~{\pm}~22$ & --- & $112~{\pm}~21$ & $4.4~{\pm}~1.2$ \\ % \hline % ${\nu}^{*} {\rightarrow} {\nu}{Z_{{\hookrightarrow}qq}}$ & $88$ & $81~{\pm}~15$ & $54~{\pm}~13$ & $5~{\pm}~1.6$ & $22~{\pm}~5$ \\ % \hline % ${\nu}^{*} {\rightarrow} {\nu}{\gamma}$ & $12$ & $11.6~{\pm}~2.5$ & $9.1~{\pm}~2.4$ & $1.3~{\pm}~0.3$ & $0.4~{\pm}~0.15$ \\ % \hline % \end{tabular} % \end{center} % \caption{Observed and predicted event yields for the $\nu\gamma$, ${\nu}{Z_{{\hookrightarrow}q\bar{q}}}$, ${e}{W_{{\hookrightarrow}q\bar{q}}}$ event classes. % The analysed data sample corresponds to an integrated luminosity of 114 pb$^{-1}$. % The errors on the prediction include model uncertainties and experimental systematic errors added in quadrature.} % \label{tab:nustaryields} % \end{table} % \begin{table}[] % \begin{center} % \begin{tabular}{|c||c|c||c|c|c|c|c|} % \multicolumn{8}{c}{Search for $\nu^*$, HERA I+II ($e^{-}p$, 184 pb$^{-1}$, preliminary)}\\ % \hline % Selection & Data & SM & CC DIS & NC DIS & $\gamma p$ & W & $l$-pair\\ % \hline % ${\nu}^{*} {\rightarrow} {\nu}{\gamma}$ & $9$ & $15~{\pm}~4$ & $12$ & $1$ & $1.0$ & $1.1$ & $0.1$ \\ % \hline % ${\nu}^{*} {\rightarrow} {e}{W_{{\hookrightarrow}qq}}$ & $198$ & $189~{\pm}~33$ & --- & $180$ & $7$ & $2$ & --- \\ % \hline % ${\nu}^{*} {\rightarrow} {\nu}{Z_{{\hookrightarrow}qq}}$ & $111$ & $102~{\pm}~24$ & $75$ & $6$ & $20$ & $1$ & --- \\ % \hline % ${\nu}^{*} {\rightarrow} {e}{W_{{\hookrightarrow}\nu\mu}}$ & $0$ & $0.54~{\pm}~0.04$ & --- & $0.01$ & --- & $0.17$ & $0.36$ \\ % \hline % ${\nu}^{*} {\rightarrow} {e}{W_{{\hookrightarrow}{\nu}e}}$ & $0$ & $0.6~{\pm}~0.3$ & --- & $0.3$ & --- & $0.3$ & --- \\ % \hline % ${\nu}^{*} {\rightarrow} {\nu}{Z_{{\hookrightarrow}ee}}$ & $0$ & $0.12~{\pm}~0.04$ & --- & $0.03$ & --- & $0.07$ & $0.02$ \\ % \hline % \end{tabular} % \end{center} % \begin{table}[] \begin{center} \begin{tabular}{|c||c|c||c|} \multicolumn{4}{c}{Search for $\nu^*$, HERA I+II ($e^{-}p$, 184 pb$^{-1}$, preliminary)}\\ \hline Selection & Data & SM & Efficiency $\times$ BR\\ \hline ${\nu}^{*} {\rightarrow} {\nu}{\gamma}$ & $9$ & $15~{\pm}~4$ & $50$ \%\\ \hline ${\nu}^{*} {\rightarrow} {e}{W_{{\hookrightarrow}qq}}$ & $198$ & $189~{\pm}~33$ & $30$--$40$ \%\\ \hline ${\nu}^{*} {\rightarrow} {\nu}{Z_{{\hookrightarrow}qq}}$ & $111$ & $102~{\pm}~24$ & $40$ \%\\ \hline ${\nu}^{*} {\rightarrow} {e}{W_{{\hookrightarrow}\nu\mu}}$ & $0$ & $0.54~{\pm}~0.04$& $3$--$4.5$ \%\\ \hline ${\nu}^{*} {\rightarrow} {e}{W_{{\hookrightarrow}{\nu}e}}$ & $0$ & $0.6~{\pm}~0.3$ & $4$--$6$ \% \\ \hline ${\nu}^{*} {\rightarrow} {\nu}{Z_{{\hookrightarrow}ee}}$ & $0$ & $0.12~{\pm}~0.04$ & $2$ \%\\ \hline \end{tabular} \end{center} \caption{Observed and predicted event yields for the studied decay channels. The analysed data sample corresponds to an integrated luminosity of 184 pb$^{-1}$. The errors on the prediction include model uncertainties and experimental systematic errors added in quadrature.} \label{tab:nustaryields} \end{table} % \begin{figure}[htbp] % \begin{center} % \includegraphics[width=7.5cm]{/usr/people/trinh/fig_nustar/fig06_H1Preliminary/BR_mf_11.eps} % \includegraphics[width=7.5cm]{/usr/people/trinh/fig_nustar/fig06_H1Preliminary/BR_pf_11.eps} % \end{center} % \caption{The branching ratios for excited neutrinos as a function of the mass of excited neutrinos. The assumptions $f = -f'$ (left) and $f = +f'$ (right) are made respectively. The branching ratios for the different decay channels are shown separately (red, blue, green lines corresponding to $\nu\gamma$, $eW$, $\nu{Z}$) and the total branching ration of analysed decay channels are shown by the black line.} % \label{fig:Branching} % \end{figure} \begin{figure}[htbp] % \begin{center} \includegraphics[width=.5\textwidth]{./H1prelim-07-066.fig1.eps}\put(-10,37) {{\bf (a)}} \includegraphics[width=.5\textwidth]{./H1prelim-07-066.fig3.eps}\put(-10,37) {{\bf (b)}}\\ \includegraphics[width=.5\textwidth]{./H1prelim-07-066.fig2.eps}\put(-10,37) {{\bf (c)}} %\end{center} \caption{Invariant mass distribution of the $\nu^*$ candidates for the (a) ${\nu}^{*} {\rightarrow} {\nu}{\gamma}$, (b) ${\nu}^{*} {\rightarrow} {\nu}{Z_{{\hookrightarrow}q\bar{q}}}$ and (c) ${\nu}^{*} {\rightarrow} {e}{W_{{\hookrightarrow}q\bar{q}}}$ searches. The points corresponds to the observed data events in the final selections and the histogram to the total SM prediction. The error bands on the SM prediction include model uncertainties and experimental systematic errors added in quadrature.} \label{fig:Mass} \end{figure} \begin{figure}[htbp] \begin{center} % \includegraphics[width=7.5cm]{./H1prelim-06-062.fig4.eps} % \includegraphics[width=7.5cm]{./H1prelim-06-062.fig5.eps} \includegraphics[width=.5\textwidth]{H1prelim-07-066.fig4.eps}\put(-10,50){{\bf (a)}} \includegraphics[width=.5\textwidth]{H1prelim-07-066.fig5.eps}\put(-10,50){{\bf (b)}} \end{center} \caption{Exclusion limits on the coupling $f/\Lambda$ at 95\% C.L. as a function of the mass of the excited neutrino with the assumptions (a) $f = -f'$ and (b) $f = +f'$. The observed limits from this analysis using all H1 $e^-p$ data is represented by the yellow area. Values of the couplings above the curves are excluded. The orange-dark area corresponds to the exclusion domain published by the H1 experiment \protect{\cite{Adloff:2001me}} using 98/99 data and the dashed line to the exclusion limit from the L3 experiment at LEP \protect{\cite{Acciarri:2000}}. } \label{fig:LimitCoupling} \end{figure} \end{document}