%================================================================ % 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.} \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} \begin{small} \begin{tabular}{llrr} Prepared for the & & & \epsfig{file=/h1/www/images/H1logo_bw_small.epsi ,width=2.cm} \\[.2em] \hline \multicolumn{4}{l}{{\bf 14th International Workshop on Deep Inelastic Scattering, DIS2006, April 20-24, 2006, Tsukuba, Japan}} \\ % & Abstract: & {\bf xx-xxx} &\\ % & Parallel Session & {\bf x} &\\ \hline & \multicolumn{3}{r}{\footnotesize {\it % www-h1.desy.de/h1/www/publications/conf/conf\_list.html}} \\[.2em] www-h1.desy.de/publications/H1preliminary.short\_list.html}} \\[.2em] & \multicolumn{3}{r}{H1prelim-06-062} \\[.2em] \end{tabular} \end{small} \end{center} \vspace*{2cm} \begin{center} \begin{Large} %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% {\bf \boldmath 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 $e^{-}p$~data collected in 2005 by the H1 experiment at HERA at center-of-mass energy of 318 GeV with an integrated luminosity of 114~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 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} %\clearpage % % % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % \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 lowe % % % % 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 correspond 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. The subsequent W and Z gauge boson decays considered are those involving jets. % % % % This paper is organized as follows. The phenomenological model used to interpret the results of the search for excited fermions is discussed in section 2. The generators used for the Monte Carlo simulation of the Standard Model events and excited neutrinos signals are briefly presented in section 3. The event selection and comparaison with standard model expectation for three decay channels are described in section 4. The mass reconstruction of excited neutrinos is presented in section 5. The most imp % % % % % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % \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 % % % % 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 for % % % % % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % \section{Monte Carlo simulation} % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % % % Final states of events selection in this analysis contain either a high energy electron (or photon) or jets with high tranverse energy (or missing transverse momentum). The main backgrounds from Standard Model processes which could minic such signatures are neutral current deep inelastic scattering (NC DIS), charged current deep inelastic scattering (CC DIS), photoproduction processes, QED Compton scattering and W and Z production. % % % % The program RAPGAP~\cite{Jung:1995} was used to simulate backgrounds from neutral and charged current deep inelastic scattering. RAPGAP includes QED first order radiative corrections based on HERACLES~\cite{Heracles:1992} and includes the leading order QCD matrix element and high order radiative correction modelling by leading-log parton showers. In which, the parton densities in the proton are taken from the CTEQ5L parametrization which includes constraints from DIS measurements at HERA up to squared % % % % Backgrounds from elastic and quasi-elastic QED-Compton Scattering were simulated with the WABGEN~\cite{Carli:1992} generator. Resolved and direct photoproduction (PHP) backgrounds were simulated with the HERWIG 5.9~\cite{Marchesini:1992} generator. PHYTHIA 6.1~\cite{Phythia:2001} was used to simulate backgrounds from the photoproduction of promt photons. Light and heavy flavoured jets are generated. The simulation contains the Born level hard scattering matrix elements and radiative QED corrections. T % % % % 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. In which, the initial state radiation of a photon from the incoming electron is generated. The photon is taken to be collinear with the electron, with an energy spectrum given by the Weizsack % % % % All simulated events were passed through the full GEANT~\cite{Geant} based simulation of the H1 appaatus, which takes into account the running conditions of the different data taking periods. % % % % % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % \section{Excited-Neutrino Event Selection} % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % % % 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 isolate % % % % The selection criteria adapted to the different event topologies are described below: % % % % \subsection{The ${\nu}^{*} {\rightarrow} {\nu}{\gamma}$ channel} % % For this analysis events containing one photon with $P_{T}^{\gamma} > 20$~GeV and $5^{\circ} < {\theta}^{\gamma} < 120^{\circ}$ and satisfying $P_{T}^{miss} > 15$~GeV and E-Pz $<$ 65~GeV. Candidates are selected if they satisfy $log(Q_{e}^{2} > 3.5)$~GeV$^{2}$. This cut on the logarit of quadred momentum transverse aim to reduce CC DIS background. And if the event has E-Pz $>$ 45~GeV we ask the photon momentum to be below 40 GeV. This criteria aim also to anti-CC. The final state for the signal contai % % \subsection{The ${\nu}^{*} {\rightarrow} {\nu}Z_{{\hookrightarrow}qq}$ and ${\nu}^{*} {\rightarrow} eW_{{\hookrightarrow}qq}$ channels} % % The analysis for these channels uses a subsample of events with at least to jets each having a high transverse momentum ($P_{T}^{j1,2} > 20,15$~GeV) and a polar angle between $5^{\circ}$ and $130^{\circ}$. The jet-jet invariant mass must be compatible with the revelant boson mass. When more than two jets are found in an event, the pair of jets which has an invariant mass closest to the revelant boson mass is selected. % % \subsubsection{The ${\nu}^{*} {\rightarrow} {\nu}Z_{{\hookrightarrow}qq}$: Events with two high $P_{T}^{jets}$ and missing $P_{T}$} % % In this channel, the main background which is due to CC DIS interactions is suppressed by the $P_{T}^{miss} > 12$~GeV cut and E-Pz $<$ 65~GeV. In addition, the quadred momentum transverse must to be of 150 GeV ($Q_{h}^{2} > 150$~GeV). The NC DIS background is reduced by rejecting events possessing an electromagnetic cluster and the missing momentum of 40 GeV if the munber of jets is found at least 3. The photoproduction background is removed by requiring the hadronic having a high transverse momentum % % \subsubsection{The ${\nu}^{*} {\rightarrow} eW_{{\hookrightarrow}qq}$ : Events with two high $P_{T}^{jets}$ and one electron} % % This channel is characterized by two high $P_{T}$ jets and an electron. Background events are expected from NC DIS. Candidates are selected if they have an electron with $P_{T}^{e} > 10$~GeV and with $5^{\circ} < \theta^{e} < 90^{\circ}$ and the polar angle of the fisrt jet attributted to the decay of the W boson must be below $80^{\circ}$. The cut on the polar angle of the electron and the first jet discriminates the signal, where the electron is mainly emitted in the forward direction due the high $ % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % \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 in figure~\ref{fig:Resolution}. The resolutions for the $\nu\gamma$, $eW$ channels are better than for the $\nu{Z}$. % % % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % \section{Systematic uncertainties} % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % % % The most important sources of systematic uncertainty were: % % \begin{description} % % \item[$\bullet$] the theoretical incertainty on the production cross-section due to radiative corrections to the excited-fermion production model and to the uncertainties on the parton densities in the proton was taken to be 8\%, as determined from an earlier study~\cite{Derrick:1995}. % % \item[$\bullet$] the acceptance was determined using a simulation of spin-1/2 excited fermions. To estimate the effect of models assuming other spin state, the variation of the acceptance was evaluated by changing the nominal decay-angle distribution to an istropic one~\cite{Derrick:1995}. The variation was typically 5\% or less. % % \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 trigger was varied of 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} % % % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % \section{Results} % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % % % 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 1 with the expected backgrounds for the ${\nu}^{*}$. The agreement with the SM prediction is good. No evidence for a resonance is seen. The events corresponding with the high $M_{\nu\gamma}$, $M_{\nu{Z}}$, $M_{eW}$ invariant mass are shown in figure~\ref{fig:Mass}. % % Since there is no evidence for excited neutrinos, upper limits at 95\% confidence level on cross-section and $f/{\Lambda}$ were derived. % % % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % \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 % % % % 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 ${\nu}^{*}$, assuming $f = -f'$ and $f = +f'$. In particular when $f = +f'$ the ${\nu}^{*} {\rightarrow} {\nu}{\gamma}$ is forbidden. % % % % 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:LimitCoupling} shows for comparation results obtained by the ZEUS collabaration in $e^{-}p$ collisons at center of mass energies up to 318 GeV at HERA. The H1 limits are more stringent at high masses beond the kinematic reach og LEP II. % % % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % \section{Summary} % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % % % Using $e^{-}p$ data collected in 2005 with an integral luminosity of 114~pb$^{-1}$~a search for the production of excited neutrionos has been performed. The events 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 bees 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 $f'$. % % % % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % % \section{Acknowledgements} % % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % % We are grateful to the HERA machine group whose outstanding efforts have made and continue to make this experiment possible. We thank the engineers and technicians for their work in constructing and now maintaining the H1 detector, our funding agencies for financial support, the DESY technical staff for continual assistance and the DESY directorate for the hospitality which they extend to the non DESY members of the collaboration. % % % % % % % \newpage % % % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % \newpage % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % \begin{thebibliography}{99} % % % % \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{Baur:1990} % % U.~Baur,M M.~Spira and P.~M.~Zerwas, Phys.\ Rev. {\bf D 42} (1990) 815. % % % % \bibitem{Hagiwara:1985} % % K.~Hagiwara, S.~Komamiya and D.~Zeppenfeld, Z.~Phys.\ {\bf C 29} (1985) 115. % % % % \bibitem{Abe:1997} % % F.~Abe {\it et all.} [CDF Collaboration] % % Phys.\ Rev.\ {\bf D 55} (1997) 5263 % % % % \bibitem{Jung:1995} % % H.~Jung, Comp.~Phys.\ Commun, {\bf 86} (1995) 147, Version 2.06, http://www-h1.desy.de/~jung/rapgap.html % % % % \bibitem{Heracles:1992} % % HERACLES 4.4: A.~KniatKnowski, H.Spiesberger and H-J Moring, Comp.Phys.\ Compnun. {\bf 69} (1992) 155. % % % % \bibitem{Martin:1998} % % A.~D.~Martin, R.~G.~Roberts, W.~J.~Stirling and R.~S.~Thorne, Eur.\ Phys.\ J.~{\bf C 4} (1998) 463. % % % % \bibitem{H1Collaboration:1996} % % H1 Collaboration, S.~Aid {\it et al.}, Nucl.\ Phys.~{\bf B 470} (1996) 3. % % % % \bibitem{Zeus:1996} % % ZEUS Collaboration, M.~Derrick {\it et al.}, Z.\ Phys. {\bf C 72} (1996) 399. % % % % \bibitem{Jetset:1994} % % JETSET 7.3 and 7.4: T.~Sjostrand, Lund Univ.~preprint LU-TP-95-20 (August 1995) 321pp;ibid, CERN preprint TH-7112-93 (Ferbruary 1994) 305pp. % % % % \bibitem{Derrick:1995} % % ZEUS Collaboration, M.~Derrick {\it et al.}, Z.\ Phys.\ J.~{\bf C 65} (1995) 627. % % % % \bibitem{Carli:1992} % % C.~Berger and P.~Kandel, Prepared for WorkShop on Monte Carlo Generators for HERA Physics Hamburg, Germany,27-30 Apr 1998. % % % % \bibitem{Phythia:2001} % % T.~Sjostrand {\it et al.}, Comput.\ Phys.\ Commun.~{\bf 135} (2001) 238 [hep-ph/0010017]. % % (The PARP(67) parameter was set to 4 instead of its defaut value of 1). % % % % \bibitem{Marchesini:1992} % % G.~Marchesini {\it et al.}, Comp.\ Phys.\ Comm. 67 (1992) 465. % % % % \bibitem{Baur:1992} % % U.~Baur, J.A.M. Vermaseren and D.Zeppenfeld, Nucl.\ Phys. {\bf B 375} 3. % % % % \bibitem{Diener:2002} % % K.~P.~Diener, C.~Schwanenberger and M.~Spira, Eur.\ Phys.\ J.~{\bf C 25} (2002) 405 [hep-ph/0203269]. % % % % \bibitem{Diener} % % K.~P.~Diener, C.~Schwanenberger and M.~Spira, [hep-ph/0302040]. % % % % \bibitem{grape:2001} % % T.~Abe, Comput.\ Phys.\ Commun.~{\bf 136} (2001) 126 [hep-ph/0012029]. % % % % \bibitem{Geant} % % R.~Brun, F.~Bruyant, M.~Maire, A.~C.~McPherson and P.~Zanarini, CERN-DD/EE/84-1. % % % % \bibitem{Phythia:2002} % % T.~Sjostrand, P.~Eden, C.~Friberg, L.~Lonnblad, G.Miu. S.Mrenna and E.~Norrbin, Computer Physics Commun, {\bf 135} 238 [hep-ph/0108264] % % % % \bibitem{Ellis:1993} % % S.~D.~Ellis and D.~E.~Soper, Phys.\ Rev.~{\bf D 48} (1993) 3160 [hep-ph/9305266]. % % % % \bibitem{Catani:1993} % % S.~Catani, Y.~L.~Dokshitzer, M.~H.~Seymour and B.~R.~Webber, Nucl.\ Phys. {\bf B 406} (1993) 187. % % % % \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 % % % % % \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 $\nu\gamma$, ${\nu}{Z_{{\hookrightarrow}qq}}$, ${e}{W_{{\hookrightarrow}qq}}$ 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{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=7.5cm]{./H1prelim-06-062.fig1.eps} \includegraphics[width=7.5cm]{./H1prelim-06-062.fig3.eps} \\ \includegraphics[width=7.5cm]{./H1prelim-06-062.fig2.eps} \end{center} \caption{Invariant mass distributions for the (a)${\nu}^{*} {\rightarrow} {\nu}{\gamma}$, (b) ${\nu}^{*} {\rightarrow} {\nu}{Z_{{\hookrightarrow}qq}}$ and (c) ${\nu}^{*} {\rightarrow} {e}{W_{{\hookrightarrow}qq}}$ searches. The points corresponds to the observed data events in the final selections and the yellow histogram to the total SM prediction.} \label{fig:Mass} \end{figure} % % \begin{figure}[htbp] % \begin{center} % \includegraphics[width=8cm]{/usr/people/trinh/fig_nustar/Efficacite_040306.eps} % \end{center} % \caption{Excited neutrinos selection efficiency in each decay channel (the red line is for the $\nu\gamma$, the green line is for the $\nu{Z_{{\hookrightarrow}qq}}$ and the blue is for the $eW_{{\hookrightarrow}qq}$).} % \label{fig:Efficiency} % \end{figure} % % \begin{figure}[htbp] % \begin{center} % \includegraphics[width=7.5cm]{/usr/people/trinh/fig_nustar/fig06_H1Preliminary/SignalResolution_NuG.eps} % \includegraphics[width=7.5cm]{/usr/people/trinh/fig_nustar/fig06_H1Preliminary/SignalResolution_NuW.eps}\\ % \includegraphics[width=7.5cm]{/usr/people/trinh/fig_nustar/fig06_H1Preliminary/SignalResolution_NuZ.eps} % \end{center} % \caption{Gaussian mass resolutions are shown for the $\nu\gamma$ (left top), the $eW$ (right top) and the $\nu{Z}$ (bottom) channels. The better resolution are $\nu\gamma$ and $eW$ channels. The worse resolution is for the $\nu{Z}$ channel.} % \label{fig:Resolution} % \end{figure} % % \begin{figure}[htbp] % \begin{center} % \includegraphics[width=7.5cm]{/usr/people/trinh/fig_nustar/fig06_H1Preliminary/cross_section_BR_mf_11_new.eps} \includegraphics[width=7.5cm]{/usr/people/trinh/fig_nustar/fig06_H1Preliminary/cross_section_BR_pf_11_new.eps} % \end{center} % \caption{Expected and observed upper limits at 95\% Confidence Level on the product ot the production cross-section ${\sigma}$ and the decay branching fraction BR for excitted beutrinos ${\nu}^{*}$ in the various electroweak decay channels, $\nu\gamma$ (red line), $\nu{Z}$ (green line) and $eW$ (blue line) as a function of the excited neutrino mass. The different decay channels of the W and Z gauge bosons are combined. Areas above the curves are excluded.} % \label{fig:LimitCrosssection} % \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} \end{center} \caption{Exclusion limits on $f/\Lambda$ at 95\% C.L. as a function of the mass of the excited neutrino. The assumptions $f = -f'$ and $f = +f'$ are made for figure (a) and (b) respectively. The observed limits from this analysis using 2005 $e^-p$ data is represented by the yellow area. Values of the couplings above the curves are excluded. The orange area corresponds to the exclusion domain published by the H1 experiment using 98/99 data and the violet-dashed line to exclusion limit from the L3 experiement at LEP. } \label{fig:LimitCoupling} \end{figure} \end{document}