共查询到20条相似文献,搜索用时 31 毫秒
1.
Jonathan R. Gaunt Chun-Hay Kom Anna Kulesza W. James Stirling 《The European Physical Journal C - Particles and Fields》2010,69(1-2):53-65
We study the production of same-sign W boson pairs at the LHC in double parton interactions. Compared with simple factorised double parton distributions (dPDFs), we show that the recently developed dPDFs, GS09, lead to non-trivial kinematic correlations between the W bosons. A numerical study of the prospects for observing this process using same-sign dilepton signatures, including W ± W ± jj, diboson and heavy flavour backgrounds, at 14 TeV centre-of-mass energy is then performed. It is shown that a small excess of same-sign dilepton events from double parton scattering over a background dominated by single scattering W ± Z(γ *) production could be observed at the LHC. 相似文献
2.
3.
T. Åkesson M. G. Albrow S. Almehed O. Benary H. Bøggild O. Botner H. Breuker A. A. Carter J. R. Carter Y. Choi W. E. Cleland S. Dagan E. Dahl-Jensen I. Dahl-Jensen G. Damgaard C. W. Fabjan U. Goerlach K. H. Hansen V. Hedberg G. Jarlskog S. Katsanevas N. J. Kjaer R. Kroeger K. Kulka D. Lissauer B. Lörstad A. Markou N. A. McCubbin U. Mjörnmark R. Møller B. S. Nielsen L. Olsen Y. Oren J. Schukraft K. Spang H. Specht M. Sullivan H. H. Thodberg J. A. Thompson E. Vella J. Williamson W. J. Willis The Axial Field Spectrometer Collaboration 《Zeitschrift fur Physik C Particles and Fields》1987,34(2):163-174
In a study ofpp collisions at \(\sqrt s = 63\) GeV with more than 29 GeV total transverse energy emitted into 1.8 units of rapidity in the central region, we have extracted a sample of 4-jet events and compared it with models of the two sources of 4-jet production: double bremsstrahlung and double parton scattering. The data cannot be described by bremsstrahlung alone, and we extract the fraction of 4-jet events attributed to double parton scattering for various definitions of the 4-jet sample. We determine the double parton scattering/2-jet yield ratio, and this leads to a determination of the proton radius. We discuss the implications of our observations for the general understanding of high-ΣE T events. 相似文献
4.
Fran?ois Arleo 《The European Physical Journal C - Particles and Fields》2009,61(4):603-627
We discuss some of the recent advances in the field of parton fragmentation processes into hadrons as well as their possible
modifications in QCD media. Hadron-production data in e
+
e
−, deep inelastic scattering and hadronic collisions are presented, together with global analyses of fragmentation functions
into light and heavy hadrons and developments on parton fragmentation in perturbative QCD at small momentum fraction. Motivated
by the recent RHIC data indicating a significant suppression of large-p
⊥
hadron production in heavy-ion collisions, several recent attempts to model medium-modified fragmentation, e.g. by solving
“medium” evolution equations or through Monte Carlo studies, have been proposed and are discussed in detail. Finally, we mention
the possibility to extract medium-modified fragmentation functions using photon–hadron correlations. 相似文献
5.
We argue that the recent LHCb observation of J/ψ-pair production indicates a significant contribution from double parton scattering, in addition to the standard single parton scattering component. We propose a method to measure the double parton scattering at LHCb using leptonic final states from the decay of two prompt J/ψ mesons. 相似文献
6.
Leonard P. Gamberg 《Pramana》2009,72(1):55-68
The naive time reversal odd (‘T-odd’) parton distribution and fragmentation functions are explored. We use the spectator model
framework to study flavour dependence of the Boer-Mulders (h
1⊥ ) and Sivers (f
1T⊥) functions as well as the ‘T-even’ but chiral odd function h
1L⊥. These transverse momentum-dependent parton distribution functions are of significance for the analysis of azimuthal asymmetries
in semi-inclusive deep inelastic scattering, as well as for the overall physical understanding of the distribution of transversely
polarized quarks in unpolarized hadrons. In this context we also consider the Collins mechanism and the fragmentation function
H
1⊥. As a by-product of this analysis we calculate the leading twist unpolarized cos(2ϕ) asymmetry, and sin(2ϕ) single spin asymmetry for a longitudinally polarized target in semi-inclusive deep inelastic scattering.
相似文献
7.
R. M. Godbole Sourendu Gupta J. Lindfors 《Zeitschrift fur Physik C Particles and Fields》1990,47(1):69-73
We investigate the double parton scattering production ofW ±+jets in proton colliders. At high energies an observable signal is expected from double parton collisions when events with small transverse momentumW together with two jets balancing inp T are selected. Double parton scattering is also a potentially serious background to several rare processes whose signal is aW ++W ?(→ev+jets) final state. A simplep T W cut seems to be sufficient to separate the genuineW-pair events from the double scattering background. 相似文献
8.
V. A. Petrov R. A. Ryutin A. E. Sobol M. J. Murray 《The European Physical Journal C - Particles and Fields》2012,72(2):1886
We propose a measurement of leading neutrons spectra at LHC in order to extract inclusive π
+
p and π
+
π
+ cross-sections with high p
T
jets production. The cross-sections for these processes are simulated with the use of parton distributions in hadrons. In
this work we estimate the possibility to extract parton distributions in the pion from the data on these cross-sections and
also search for signatures of fundamental differences in the pion and proton structure. 相似文献
9.
A. D. Martin W. J. Stirling R. S. Thorne G. Watt 《The European Physical Journal C - Particles and Fields》2009,63(2):189-285
We present updated leading-order, next-to-leading order and next-to-next-to-leading order parton distribution functions (“MSTW
2008”) determined from global analysis of hard-scattering data within the standard framework of leading-twist fixed-order
collinear factorisation in the
[`(MS)]\overline{\mathrm{MS}}
scheme. These parton distributions supersede the previously available “MRST” sets and should be used for the first LHC data
taking and for the associated theoretical calculations. New data sets fitted include CCFR/NuTeV dimuon cross sections, which
constrain the strange-quark and -antiquark distributions, and Tevatron Run II data on inclusive jet production, the lepton
charge asymmetry from W decays and the Z rapidity distribution. Uncertainties are propagated from the experimental errors on the fitted data points using a new dynamic
procedure for each eigenvector of the covariance matrix. We discuss the major changes compared to previous MRST fits, briefly
compare to parton distributions obtained by other fitting groups, and give predictions for the W and Z total cross sections at the Tevatron and LHC. 相似文献
10.
We present predictions of the unweighted and weighted double spin asymmetries related to the transversal helicity distribution
g
1T
and the longitudinal transversity distribution h1L^h_{1L}^{\perp}, two of eight leading-twist transverse momentum dependent parton distributions (TMDs) or three-dimensional parton distribution
functions (3dPDFs), in the polarized proton–antiproton Drell–Yan process at typical kinematics on the Facility for Antiproton
and Ion Research (FAIR). We conclude that FAIR is ideal to access the new 3dPDFs toward a detailed picture of the nucleon
structure. 相似文献
11.
《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
12.
We present studies of double longitudinal spin asymmetries in semi-inclusive deep inelastic scattering using a new dedicated Monte Carlo generator, which includes quark intrinsic transverse momentum within the generalized parton model based on the fully differential cross section for the process. Additionally we employ Bessel-weighting to the MC events to extract transverse momentum dependent parton distribution functions and also discuss possible uncertainties due to kinematic correlation effects. 相似文献
13.
A. Gasparyan J. Haidenbauer C. Hanhart K. Miyagawa 《The European Physical Journal A - Hadrons and Nuclei》2007,32(1):61-67
The prospects of utilizing the strangeness production reaction γd→K
+
Λn for the determination of the Λn low-energy scattering parameters are investigated. The spin observables that need to be measured in order to isolate the
Λn singlet (1
S
0) and triplet (3
S
1) states are identified. Possible kinematical regions where the extraction of the Λn scattering lengths might be feasible are discussed. 相似文献
14.
15.
Alejandro?Ayala Eleazar?Cuautle Isabel?Domínguez Antonio?Ortiz Guy?Pai? 《The European Physical Journal C - Particles and Fields》2009,62(3):535-540
The experimental results on transverse momentum azimuthal hadron correlations at RHIC have opened a rich field for parton
energy loss analysis in heavy-ion collisions. Recently, a considerable amount of work has been devoted to study the shapes
of the “away-side” jet which exhibit an interesting and unexpected “double hump” structure not observed in the analogous treatment
of the pp data. Driven by the possibility that the latter result might just mean that such a structure exists already in the case of
pp collisions, but that its relative intensity could be small, here we use the Event Shape Analysis to show that it is possible
to identify and select well defined event topologies in pp collisions, among which a double hump structure for the away-side jet emerges. Using two shape parameters, the sphericity
in the transverse plane and the recoil to analyze a sample of PYTHIA generated pp collisions at
GeV, we show that this structure corresponds to two jets emitted in the backward hemisphere. Finally, we show that Q-PYTHIA
qualitatively reproduces the decrease in the yield of dijet events and the increase of the double hump structure in the away
side observed in heavy-ion collisions. The implications for the treatment of parton energy loss in heavy-ion collisions are
discussed. 相似文献
16.
B. Parsamyan 《The European physical journal. Special topics》2008,162(1):89-96
In general, eight target transverse spin-dependent azimuthal modulations are allowed in semi inclusive deep inelastic scattering
of polarized leptons on a transversely polarized target. In the QCD parton model four of these asymmetries can be interpreted
within the leading order approach. Two of them, namely Collins and Sivers effects were already measured by HERMES and COMPASS
experiments. Other two leading twist and remaining four azimuthal asymmetries which can be interpreted as twist-three contributions
have been measured for the first time in COMPASS using a 160 GeV/c longitudinally polarized (P
l
}~ −0.8) muon beam and a transversely polarized 6LiD target. We present here the preliminary results from the 2002–2004 data.
on behalf of the COMPASS collaboration 相似文献
17.
Saeed Ahmad Heli Honkanen Simonetta Liuti Swadhin K. Taneja 《The European Physical Journal C - Particles and Fields》2009,63(3):407-421
We propose a physically motivated parameterization for the unpolarized generalized parton distributions, H and E, valid at both zero and non-zero values of the skewness variable, ζ. Our approach follows a previous detailed study of the
ζ=0 case where H and E were determined using constraints from simultaneous fits of the experimental data on both the nucleon elastic form factors
and the deep inelastic structure functions in the non-singlet sector. Additional constraints at ζ≠0 are provided by lattice
calculations of the higher moments of generalized parton distributions. We illustrate a method for extracting generalized
parton distributions from lattice moments based on a reconstruction using sets of orthogonal polynomials. The inclusion in
our fit of data on Deeply Virtual Compton Scattering is also discussed. Our method provides a step towards an extraction of
generalized distributions based on a global fit of the available data within the given set of constraints. 相似文献
18.
In the framework of the k
t-factorization approach, the production of γ mesons at the Fermilab Tevatron and CERN LHC is considered, and the predictions
on the spin alignment parameter a are presented. We argue that measuring the polarization of quarkonium states can serve as a crucial test discriminating two
competing theoretical approaches to parton dynamics in QCD.
The text was submitted by the authors in English. 相似文献
19.
P. Lévai G. Papp G. G. Barnaföldi G. Fai 《The European physical journal. Special topics》2008,155(1):89-99
We present our results on neutral pion (π0) production
in pp and dAu collisions at RHIC energy. Pion spectra
are calculated in a next-to-leading
order (NLO) perturbative QCD-based model.
The model includes the transverse component of the
initial parton distribution (“intrinsic kT”).
We compare our results to the available experimental data from RHIC,
and fit the data with high precision.
The calculation tuned this way is repeated for the dAu collision,
and used to investigate the interplay of shadowing and
multiple scattering at RHIC.
The centrality dependence of the nuclear modification
factor shows a measurable difference between different
shadowing parameterizations. 相似文献
20.
Svend Domdey Hans-Jürgen Pirner Urs Achim Wiedemann 《The European Physical Journal C - Particles and Fields》2010,65(1-2):153-162
The scale factor σ eff is the effective cross section used to characterize the measured rate of inclusive double dijet production in high-energy hadron collisions. It is sensitive to the two-parton distributions in the hadronic projectile. In principle, the scale factor depends on the center of mass energy and on the minimal transverse energy E T,min? of the jets contributing to the double dijet cross section. Here, we point out that proton–proton collisions at the LHC will provide for the first time experimental access to these scale dependences in a logarithmically wide, nominally perturbative kinematic range 10?E T,min??100 GeV. This constrains the dependence of two-parton distribution functions on parton momentum fractions and parton localization in impact parameter space. Novel information is to be expected about the transverse growth of hadronic distribution functions in the range of semi-hard Bjorken x (0.001?x?0.1) and high resolution Q 2. We discuss to what extent one can disentangle different pictures of the x-evolution of two-parton distributions in the transverse plane by measuring double-hard scattering events at the LHC. 相似文献