9,170 research outputs found
Proton and deuteron F_2 structure functions in deep inelastic muon scattering
Get PDFAmaudruz P, Arneodo M, Arvidson A, et al. Proton and deuteron F_2 structure functions in deep inelastic muon scattering. Phys.Lett. B. 1992;295(1-2):159-168.The structure functions F2p and F2d measured by deep inelastic muon scattering at incident energies of 90 and 280 GeV are presented. These measurements cover a large kinematic range, 0.006 less-than-or-equal-to x less-than-or-equal-to 0.6 and 0.5 less-than-or-equal-to Q2 less-than-or-equal-to 55 GeV2, and include the first precise data at small x, where large scaling violations are observed. The data agree with earlier results from SLAC and BCDMS but exhibit differences with respect to those of EMC-NA2. Extrapolations to small x of recent phenomenological parton distributions are shown to disagree with the present results
QCD analysis of deep inelastic lepton-hadron scattering in the region of small values of the bjorken parameter x
Get PDFWe present the new framework based on BFKL and DGLAP evolution equations in which the leading in(Q(_2)) and in(l/x) terms are treated on equal footing. We introduce a pair of coupled integro-difFerential equations for the quark singlet and the unintegrated gluon distribution. The observable structure functions are calculated using high energy factorisation approach. We also include the sub-leading in (l/x) effects via consistency constraint. We argue that the use of this constraint leads to more stable solution to the Pomeron intercept than that based on the NLO calculation of the BFKL equation alone and generates resummation to all orders of the major part of the subleading in (l/x) effects. The global fit to all available deep inelastic data is performed using a simple parametrisation of the non-perturbative region. We also present the results for the longitudinal structure function and the charm component of the F(_2) structure function. Next; we extend this approach to the low Q(^2) domain. At small distances we use the perturbative approach based on the unified BFKL/DGLAP equations and for large distances we use Vector Meson Dominance Model and, for the higher mass qq states, the additive quark approach. We show the results for the total cross section and for the ratio of the longitudinal and transverse structure functions. Finally, we calculate the dijet production and consider the decorrelation effects in the azimuthal distributions caused by the diffusion in the transverse momentum k(_r) of the exchanged gluon. Using the gluon distribution which is fixed by the fit to the DIS data we are able to make absolute predictions. We show the results for the dF(_r)/dɸ, the total cross section and also the distributions in Q(^2) as well as in the longitudinal momentum fraction of the gluon. Our theoretical predictions are confronted with the measurements made using ZEUS detector at HERA
Transverse momentum dependent multiplicities of hadrons produced in DIS at COMPASS
Get PDFThe COMPASS Collaboration measured the transverse momentum dependent multiplicities of charged hadrons produced in Deep Inelastic Scattering (DIS) off unpolarized protons. Complementing previous COMPASS measurements obtained with an isoscalar target, the data have been collected in 2016 and 2017 with 160 GeV/ muon beams and a liquid hydrogen target. The multiplicities are studied as a function of the square of the hadron transverse momentum with respect to the virtual photon direction in bins of the Bjorken variable , of the photon virtuality and of the fraction of the photon energy carried by the hadron. Preliminary results of this analysis, performed on a fraction of the available data sample, are shown here for the first time.The COMPASS Collaboration measured the transverse momentum dependent multiplicities of charged hadrons produced in Deep Inelastic Scattering (DIS) off unpolarized protons. Complementing previous COMPASS measurements obtained with an isoscalar target, the data have been collected in 2016 and 2017 with 160 GeV/ muon beams and a liquid hydrogen target. The multiplicities are studied as a function of the square of the hadron transverse momentum with respect to the virtual photon direction in bins of the Bjorken variable , of the photon virtuality and of the fraction of the photon energy carried by the hadron. Preliminary results of this analysis, performed on a fraction of the available data sample, are shown here for the first time
Deep-inelastic electron-proton diffraction
No full textRecent measurements by the H1 collaboration at HERA of the cross section for deep-inelastic electron-proton scattering in which the proton interacts with minimal energy transfer and limited 4-momentum transfer squared are presented in the form of the contribution F_2"D"("3") to the proton structure function F_2. By parametrising the cross section phenomenologically in terms of a leading effective Regge pole exchange and comparing the result with a similar parametrisation of hadronic pp physics, the proton interaction is demonstrated to be dominantly of a diffractive nature. The quantitative interpretation of the parametrisation in terms of the properties of an effective leading Regge pole exchange, the pomeron (IP), shows that there is no evidence for a 'harder' BFKL-motivated IP in such deep-inelastic proton diffraction. The total contribution of proton diffraction to deep-inelastic electron-proton scattering is measured to be #propor to#10% and to be rather insensitive to Bjorken-x and Q"2. A first measurement of the partonic structure of diffractive exchange is presented. It is shown to be readily interpreted in terms of the exchange of gluons, and to suggest that the bulk of diffractive momentum transfer is carried by a leading gluon. (orig.)43 refs.Available from TIB Hannover: RA 2999(95-228) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman
H1 contributions to the workshop on deep inelastic scattering and QCD, Paris'95
No full textThe following topics were dealt with: Forward jets in deep inelastic scattering at HERA, diffractive interactions, rapidity gap events at HERA and the structure of the pomeron, new results on the proton structure function from H1, extraction of the gluon density at low-x from F_2 proton dataAvailable from TIB Hannover: RA 2999(95-152) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman
Selected topics of deep inelastic scattering from the sixties to HERA
No full textThis talk reports on important steps in deep inelastic scattering, starting in the sixties before scaling violations were observed, and ending with most recent results from HERA. The selection is rather subjective and no systematic review was attempted. The emphasis is on structure functions, QCD effects in the hadronic final states and electroweak effects in electron scattering. (orig.)83 refs.Available from TIB Hannover: RA 2999(95-140) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman
Studies of final states in small x deep inelastic scattering
Get PDFWe investigate the possibility of identifying In(l/x) dynamics from studies of the final state in electron - proton deep inelastic scattering (DIS) in the small x region of the HERA collider at DESY. Motivated by recent observations at HERA we consider again the measurement of DIS events containing an identified forward jet as proposed by Mueller. We find that the shape of the x distribution of the data is described well by a prediction based on In(l/x) dynamics. Since forward jets are difficult to identify and measure accurately in the experiments we suggest the study of deep inelastic events containing an energetic isolated photon. We quantify the enhancement arising from the leading In(l/x) gluon emissions with a view to using such events to identify the underlying dynamics in the small x regime at HERA. To overcome the small event rate of jet + γ we propose that the forward jet may alternatively be identified through a single energetic decay product, the π . We investigate the feasibility of utilizing these deep inelastic + forward π events as an indicator of the small x dynamics. Motivated by this study the HI collaboration recently performed a DIS + π measurement. Therefore we update our BFKL prediction imposing the HI cuts in the calculation. We fix the normalisation by comparing with HERA data for DIS + jet. Finally we study the transverse momentum (pr) spectrum of charged particles produced in DIS at small Bjorken x in the central region between the current jet and the proton remnants. Again we normalize the BFKL prediction by comparing with the H1 DIS + jet data. We calculate the spectrum at large pr with the BFKL ln(l/x) resummation included and then repeat the calculation with it omitted. We find that data favour the former
Multi-Jet Merging in Deep Inelastic Scattering with Pythia
No full textWe aim to improve the modelling of deep inelastic scattering by implementing multi-jet merging capabilities in Vincia parton shower in the general-purpose Monte Carlo event generator, Pythia. Merging allows to combine event samples of different parton multiplicities with logarithmically enhanced radiation from parton shower algorithms, without double-counting. Here we consider events up to five outgoing partons and present results for jet analyses compared to experimental data provided by the ZEUS and H1 collaborations of the HERA collider. The analyses span a wide range in photon virtuality, and the results show that the multi-jet merging improves jet modelling especially for low virtuality events.peerReviewe
Observable jets in deep inelastic scattering as a probe of small x dynamics
Get PDFThe observation of the underlying small x dynamics arising from the resummation of large terms in In 1/x QCD descriptions of the gluon distribution have been searched for ill deep inelastic scattering experiments at the electron proton collider HERA since the early 1990's. It has been recognized that the first fully inclusive measurements of the proton structure function F2 are too inclusive to identify underlying dynamics. Less inclusive quantities need to be considered. In this thesis a modified form of the BFKL equation is derived which enables the structure of the gluon emissions to be studied in small x deep inelastic scattering. The equation incorporates the resummation of the virtual and unresolved real gluon emissions and is solved to calculate the number of small x deep-inelastic events containing 0,1,2...resolved gluon jets, that is jets with transverse momenta qr > µ. We study the jet decomposition for different choices of the jet resolution parameter to look for possible signatures of BFKL dynamics in the x dependence of the exclusive observable quantities of the n-jet contributions to F(_2).We also study the application of the BFKL equation to forward jet events at HERA. We calculate the rate of deep inelastic scattering events containing two forward jets adjacent to the proton remnants and compare with the production rate of only one forward jet - the so-called Mueller process. We obtain a stable prediction for this two to one jet ratio, which may serve as a measure of the BFKL vertex function
Parton distributions
Get PDFParton distributions, α(χ,μ(^₂) are essential ingredients for almost all theoretical calculations at hadron colliders. They give the number densities of the colliding par- tons (quarks and gluons) inside their parent hadrons at a given momentum fraction χand scale μ(^₂). The scale dependence of the parton distributions is given by DGLAP evolution, while the X dependence must be determined from a global analysis of deep-inelastic scattering (DIS) and related hard-scattering data. In Part I we introduce ‘doubly-unintegrateď parton distributions, fa(x, z, k(^₂),μ(^₂)), which additionally depend on the splitting fraction z and the transverse momentum (k) associated with the last evolution step. We show how these distributions can be used to calculate cross sections for inclusive jet production in DIS and compare the predictions to data taken at the HERA ep collider. We then calculate the transverse momentum distributions of พ and z bosons at the Tevatron pp collider and of Standard Model Higgs bosons at the forthcoming LHC. In Part II we study diffractive DIS, which is characterised by a large rapidity gap between the slightly deflected proton and the products of the virtual photon dissociation. We perform a novel QCD analysis of recent HERA data and extract diffractive parton distributions. The results of this analysis are used to investigate the effect of absorptive corrections in inclusive DIS. These absorptive corrections are due to the recombination of partons within the proton and are found to enhance the size of the gluon distribution at small X. We discuss the problem that the gluon distribution decreases with decreasing X at low scales while the sea quark distribution increases with decreasing X, whereas Regge theory predicts that both should have the same small-X behaviour. Our study hints at the possible importance of power corrections at low scales of around 1 GeV
- …
