共查询到20条相似文献,搜索用时 15 毫秒
1.
M. Diehl 《Zeitschrift fur Physik C Particles and Fields》1995,66(1-2):181-193
We investigate the production of a quark-antiquark pair in diffractive photon-proton scattering, approximating soft pomeron exchange by the exchange of two nonperturbative gluons. In deep inelastic scattering at HERA, events with two jets and the scattered proton in the final state are predicted to be observable, with an important contribution from charm production. For photoproduction of light quark jets with high transverse momentum we find that both exchanged gluons must have a large invariant mass, so that the cross section is very small, whereas for charm quarks it is quite appreciable. From our calculation we also extract the quark structure function of the pomeron for the scaling variablez no too close to 0 or 1, finding a strong flavour dependence and a behaviour somewhat harder thanz(1?z) for light quarks. 相似文献
2.
C.T. Sachrajda 《Physics letters. [Part B]》1978,76(1):100-104
We calculate the cross section for the process quark + quark → quark (with large transverse momentum) + anything, up to order g6 in the cross section and in the leading-logarithm approximation. The result is suggestive of a simple ansatz for the calculation of the asymptotic behaviour of cross sections for the production of particles or jets with large transverse momenta. 相似文献
3.
We propose to test perturbative QCD(pQCD) in the Regge limit by means of diffractive photon scattering, , at large and very high energies, . The helicity amplitudes of this process were calculated using the Lipatov solution of the BFKL equation for . We found that the perturbatively calculated cross section for this process is comparable in magnitude to the cross section
for photoproduction assuming similar kinematics.
Received: 9 September 1998 / Revised version: 2 October 1998 / Published online: 14 January 1999 相似文献
4.
A. Gehrmann-De Ridder G. Kramer H. Spiesberger 《The European Physical Journal C - Particles and Fields》1999,11(1):137-144
We study the production of photons accompanied by jets in large- deep inelastic scattering. Numerical results for the cross section differential with respect to the fraction of momentum
carried by a photon inside a jet at large , up to in perturbative QCD, are presented. The sensitivity to the fragmentation contribution allows one to study the quark-to-photon
fragmentation function. Our results can be confronted with future experimental data from HERA.
Received: 9 August 1999 / Published online: 28 September 1999 相似文献
5.
We explore the possibility to observe hard exclusive three-jet production in early LHC runs, corresponding to diffractive dissociation of the incident proton into three jets with large but compensating transverse momenta. This process is sensitive to the proton unintegrated gluon distribution at small x and to the distribution of the three valence quarks in the proton at small transverse distances. The corresponding cross section is calculated using an approach based on kt factorization. According to our estimates, observation of hard diffractive three-jet production at LHC is feasible for jet transverse momenta q⊥∼5 GeV. 相似文献
6.
S.V. Goloskokov 《The European Physical Journal C - Particles and Fields》1999,11(2):309-316
We calculate the cross section and asymmetry of the diffractive J/ leptoproduction for a simple model of a Pomeron coupling with a proton, which contains the term and a spin-dependent part. It is shown that the asymmetry caused by the Pomeron coupling does not vanish for nonzero . The sensitivity of the polarized diffractive J/ production to the spin-dependent part of the Pomeron coupling is found to be rather weak. As a result, it is difficult to
study the structure of the Pomeron coupling with the proton in future polarized diffractive experiments on the J/ production.
Received: 27 April 1999 / Revised version: 29 June 1999 / Published online: 14 October 1999 相似文献
7.
We derive the nonlinear k
⊥ factorization for the spectrum of jets in high-mass diffractive deep inelastic scattering as a function of three hard scales—the
virtuality of the photon Q
2, the transverse momentum of the jet, and the saturation scale Q
A
. In contrast to all other hard reactions studied so far, we encounter a clash between the two definitions of the glue in
the pomeron from the inclusive spectrum of leading quarks and the small-β evolution of the diffractive cross section. This
clash casts a further shadow on customary applications of the familiar collinear factorization to a pQCD analysis of diffractive
deep inelastic scattering.
The text was submitted by the authors in English. 相似文献
8.
J. Bartels J. Ellis H. Kowalski M. Wüsthoff 《The European Physical Journal C - Particles and Fields》1999,7(3):443-458
We propose a simple parametrization for the deep-inelastic diffractive cross section. It contains the contribution of production to both the longitudinal and the transverse diffractive structure functions, and of the production of final states from transverse photons. We start from the hard region and perform a suitable extrapolation into the soft region.
We test our model on the 1994 ZEUS and H1 data, and confront it with the H1 conjecture of a singular gluon distribution.
Received: 30 June 1998 / Revised version: 3 September 1998 / Pulished online: 3 December 1998 相似文献
9.
The cross section for dijet photoproduction at high transverse energies is presented as a function of the transverse energies
and the pseudorapidities of the jets. The measurement is performed using a sample of ep-interactions corresponding to an integrated luminosity of 6.3 pb, recorded by the ZEUS detector. Jets are defined by applying a -clustering algorithm to the hadrons observed in the final state. The measured cross sections are compared to next-to-leading
order QCD calculations. In a kinematic regime where theoretical uncertainties are expected to be small, the measured cross
sections are higher than these calculations.
Received: 18 May 1999 / Published online: 14 October 1999 相似文献
10.
《The European Physical Journal C - Particles and Fields》2007,51(3):549-568
Measurements are presented of differential dijet cross sections in diffractive photoproduction (Q2<0.01 GeV2) and deep-inelastic scattering processes (DIS, 4<Q2<80 GeV2). The event topology is given by ep→eXY, in which the system X, containing at least two jets, is separated from a leading
low-mass baryonic system Y by a large rapidity gap. The dijet cross sections are compared with NLO QCD predictions based on
diffractive parton densities previously obtained from a QCD analysis of inclusive diffractive DIS cross sections by H1. In
DIS, the dijet data are well described, supporting the validity of QCD factorisation. The diffractive DIS dijet data are more
sensitive to the diffractive gluon density at high fractional parton momentum than the measurements of inclusive diffractive
DIS. In photoproduction, the predicted dijet cross section has to be multiplied by a factor of approximately 0.5 for both
direct and resolved photon interactions to describe the measurements. The ratio of measured dijet cross section to NLO prediction
in photoproduction is a factor 0.5±0.1 smaller than the same ratio in DIS. This suppression is the first clear observation
of QCD hard scattering factorisation breaking at HERA. The measurements are also compared to the two soft colour neutralisation
models SCI and GAL. The SCI model describes diffractive dijet production in DIS but not in photoproduction. The GAL model
fails in both kinematic regions. 相似文献
11.
V. P. Gonçalves M. V. T. Machado 《The European Physical Journal C - Particles and Fields》2003,30(3):387-394
We calculate the nuclear inclusive and diffractive cross sections for heavy quark photoproduction within a phenomenological saturation approach. The nuclear cross section is obtained by the extension of the saturation model through the Glauber-Gribov formalism. We predict large nuclear heavy quark cross sections at LHC energies.Received: 6 May 2003, Revised: 1 July 2003, Published online: 5 September 2003 相似文献
12.
The ZEUS Collaboration J. Breitweg et al. 《The European Physical Journal C - Particles and Fields》1998,5(1):41-56
Differential dijet cross sections have been measured with the ZEUS detector for photoproduction events in which the hadronic
final state containing the jets is separated with respect to the outgoing proton direction by a large rapidity gap. The cross
section has been measured as a function of the fraction of the photon () and pomeron () momentum participating in the production of the dijet system. The observed dependence shows evidence for the presence of a resolved- as well as a direct-photon component. The measured cross section
increases as increases indicating that there is a sizeable contribution to dijet production from those events in which a large fraction
of the pomeron momentum participates in the hard scattering. These cross sections and the ZEUS measurements of the diffractive
structure function can be described by calculations based on parton densities in the pomeron which evolve according to the
QCD evolution equations and include a substantial hard momentum component of gluons in the pomeron.
Received: 20 April 1998 / Published online: 2 July 1998 相似文献
13.
V.A. Khoze A.D. Martin M.G. Ryskin 《The European Physical Journal C - Particles and Fields》2002,24(4):581-587
We emphasize the importance of tagging the outgoing forward protons to sharpen the predictions for New Physics at the LHC
(such as the diffractive production of a light Higgs boson). The rescattering effects lead to a rich distinctive structure
of the cross section as a function of the transverse momenta of the protons. We show that a study of the correlations between
the proton transverse momenta for double-diffractive production of central dijets will provide a detailed check of the whole
diffractive formalism. Adopting a perturbative two-gluon structure of the Pomeron, we emphasize that quarkonium production, via Pomeron-Pomeron fusion, is strongly suppressed. This offers a favourable production mechanism
for non- states, such as glueballs.
Received: 15 March 2002 / Published online: 21 June 2002 相似文献
14.
《The European Physical Journal C - Particles and Fields》2007,52(4):813-832
The production of dijets in diffractive deep inelastic scattering has been measured with the ZEUS detector at HERA using an
integrated luminosity of 61 pb-1. The dijet cross section has been measured for virtualities of the exchanged virtual photon, 5 < Q2 < 100 GeV2, and γ*p centre-of-mass energies, 100 < W < 250 GeV. The jets, identified using the inclusive kT algorithm in the γ*p frame, were required to have a transverse energy E*
T,jet > 4 GeV and the jet with the highest transverse energy was required to have E*
T,jet > 5 GeV. All jets were required to be in the pseudorapidity range -3.5<η*
jet<0. The differential cross sections are compared to leading-order predictions and next-to-leading-order QCD calculations based
on recent diffractive parton densities extracted from inclusive diffractive deep inelastic scattering data. 相似文献
15.
We use the transverse-momentum dependence of the cross section for the diffractive dissociation of high energy pions to two
jets to study some non-perturbative light-cone wave functions of the pion. We compare the predictions for this distribution
by Gaussian and Coulomb wave functions as well as the wave function derived from a solution of the light-cone Hamiltonian
in the singlet model. We conclude that this experimentally measured information provides a powerful tool for these studies.
Received: 15 January 2003 / Published online: 14 April 2003
RID="a"
ID="a" e-mail: ashery@tauphy.tau.ac.il
RID="b"
ID="b" e-mail: pauli@mpi-hd.mpg.de 相似文献
16.
E.R. Berger A. Donnachie H.G. Dosch W. Kilian O. Nachtmann M. Rueter 《The European Physical Journal C - Particles and Fields》1999,9(3):491-501
We investigate the reaction where PS denotes a pseudoscalar meson , , , or and X either a proton or resonance or continuum state into which the proton can go by diffractive excitation. At high energies
photon and odderon exchange contribute to the reaction. The photon exchange contribution is evaluated exactly using data for
the total virtual photon-proton absorption cross section. The odderon exchange contribution is calculated in nonperturbative
QCD, using functional integral techniques and the model of the stochastic vacuum. For the proton we assume a quark-diquark
structure as suggested by the small odderon amplitude in pp and forward scattering. We show that odderon exchange leads to a much larger inelastic than elastic PS production cross section.
Observation of our reaction at HERA would establish the soft odderon as an exchange object on an equal footing with the soft
pomeron and would give us valuable insight into both the nucleon structure and the mechanism of high energy diffractive scattering.
Received: 2 February 1999 / Revised version: 22 March 1999 / Published online: 28 May 1999 相似文献
17.
I. Akushevich 《The European Physical Journal C - Particles and Fields》1999,8(3):457-463
The electromagnetic radiative correction to the cross section of the vector meson electroproduction is calculated. Explicit
covariant formulae for the observed cross section are obtained. The dependence of the radiative correction on the experimental
resolution and on the inelasticity cut is discussed. The FORTRAN code DIFFRAD, based on both exact (ultrarelativistic) and
approximate sets of the formulae for the radiative correction to the cross section, is presented. Detailed numerical analysis
for kinematical conditions of the recent experiments on the diffractive electroproduction of vector mesons is given.
Received: 23 August 1998 / Published online: 15 April 1999 相似文献
18.
Aad G Abbott B Abdallah J Abdelalim AA Abdesselam A Abdinov O Abi B Abolins M Abramowicz H Abreu H Acerbi E Acharya BS Adams DL Addy TN Adelman J Aderholz M Adomeit S Adragna P Adye T Aefsky S Aguilar-Saavedra JA Aharrouche M Ahlen SP Ahles F Ahmad A Ahsan M Aielli G Akdogan T Åkesson TP Akimoto G Akimov AV Alam MS Alam MA Albrand S Aleksa M Aleksandrov IN Aleppo M Alessandria F Alexa C Alexander G Alexandre G Alexopoulos T Alhroob M Aliev M Alimonti G Alison J Aliyev M Allport PP 《Physical review letters》2011,106(17):172002
Azimuthal decorrelations between the two central jets with the largest transverse momenta are sensitive to the dynamics of events with multiple jets. We present a measurement of the normalized differential cross section based on the full data set (∫Ldt=36 pb(-1)) acquired by the ATLAS detector during the 2010 sqrt(s)=7 TeV proton-proton run of the LHC. The measured distributions include jets with transverse momenta up to 1.3 TeV, probing perturbative QCD in a high-energy regime. 相似文献
19.
B. Pötter 《EPJ direct》2000,1(1):1-65
We present one- and two-jet inclusive cross sections for γ*γ scattering and virtual photoproduction in ep collisions. The hard cross sections are calculated in next-to-leading order QCD. Soft and collinear singularities are extracted using the phase-space-slicing method. The initial state singularity of the virtual photon depends logarithmically its’ virtuality. This logarithm is large and has to be absorbed into the parton distribution function of the virtual photon. We define for this purpose an
factorization scheme similar to the real photon case. We numerically study the dependence of the inclusive cross sections on the transverse energies and rapidities of the outgoing jets and on the photon virtuality. The ratio of the resolved to the direct cross section in ep collisions is compared to ZEUS data. 相似文献
20.
B. Blok Yu. Dokshitzer L. Frankfurt M. Strikman 《The European Physical Journal C - Particles and Fields》2012,72(4):1963
We study production of two pairs of jets in hadron–hadron collisions in view of extracting contribution of double hard interactions of three and four partons (3→4, 4→4). Such interactions, in spite of being power suppressed at the level of the total cross
section, become comparable with the standard hard collisions of two partons, 2→4, in the back-to-back kinematics when the transverse momentum imbalances of two pairing jets are relatively small. 相似文献