H1-02/95-426 QCD Analysis from H1 F_2 C. Pascaud / LAL
Measurement F. Zomer / Paris Sud
Issues on Fitting, Statistics
and Systematic Errors
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PS file :
/afs/desy.de/group/h1/psfiles/inotes/h1-0295-426.ps
H1-01/98-536 On Parton Density Error Band G.Lobo, C.Pascaud,F.Zomer
Calculations in QCD Analysis of LAL a. Paris Sud
Proton Structure
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PS file :
/afs/desy.de/group/h1/psfiles/inotes/h1-0198-536.ps
| Abstract | The parton momentum density distributions of the proton are determined from a next-to-leading order QCD analysis of structure functions measured at HERA and by fixed target experiments. Also included are data on the difference of the up and down anti-quark distributions. The uncertainties in the parton densities, structure functions and related cross sections are estimated from the experimental errors and those on the input parameters of the fit. Several QCD predictions based on the parton densities obtained from this analysis are calculated and compared to data. |
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| Abstract | Results are presented of a study of the experimental and theoretical accuracy one may achieve at HERA in measuring the strong coupling constant alpha_s and the gluon distribution from scaling violations of F2 structure functions. |
| Paper | PS-File |
| Abstract | Preliminary results are presented on the gluon density obtained from a QCD analysis of ZEUS and NMC F2 structure function data. Also given is an estimate of the experimental error on the positron-proton NC Born cross-section at large x and Q2. |
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| Abstract | The results are presented of a study of the accuracy one may achieve at HERA in measuring the strong coupling constant alpha_s and the gluon distribution using future data of the structure function which are estimated to be accurate at the few % level over the full accessible kinematic region down to ca. and up to ca. . The analysis includes simulated proton and deuteron data, and the effect of combining HERA data with fixed target data is discussed. |
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| Abstract | Seven next-to-leading order QCD evolution programs are compared. The deviations of the results due to different theoretical prescriptions for truncating the perturbative series are clarified, and a numerical agreement between five codes of better than 0.1% is achieved. Reference results for further comparison are provided. |
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| Abstract | We present a new analysis of parton distributions of the proton. This incorporates a wide range of new data, an improved treatment of heavy flavours and a re-examination of prompt photon production. The new set (MRST) shows systematic differences from previous sets of partons which can be identified with particular features of the new data and with improvements in the analysis. We also investigate the sensitivities of the results to (i) the uncertainty in the determination of the gluon at large x, (ii) the value of and (iii) the minimum cut on the data that are included in the global fit. |
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| Abstract | The uncertainty in the calculation of many important new processes at the Tevatron and LHC is dominated by that concerning the gluon distribution function. We investigate the uncertainty in the gluon distribution of the proton by systematically varying the gluon parameters in the global QCD analysis of parton distributions. The results depend critically on the parton momentum fraction x and the QCD scale . The uncertainties are presented for integrated gluon-gluon and gluon-quark luminosities for both the Tevatron and LHC as a function of sqrt(tau)=sqrt(x1x2)=sqrt(shat/s), the most relevant quantity for new particle production. The uncertainties are reasonably small, except for large x. |
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| Abstract | Dynamical parton densities, generated radiatively from valence-like inputs at some low resolution scale, are confronted with recent small-x data on deep inelastic and other hard scattering processes. It is shown that within theoretical uncertainties our previous (1994) dynamical/radiative parton distributions are compatible with most recent data and still applicable within the restricted accuracy margins of the presently available next-to-leading order calculations. Due to recent high precision measurements we also present an updated, more accurate, version of our (valence-like) dynamical input distributions. Furthermore, our perturbatively stable parameter-free dynamical predictions are extended to the extremely small-x region, , relevant to questions concerning ultra-high-energy cosmic ray and neutrino astronomy. |
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