The impact of recent measurements of heavy-flavour production in deep inelastic
ep
scattering and in
pp
collisions on parton distribution functions is studied in a QCD analysis in the fixed-flavour ...number scheme at next-to-leading order. Differential cross sections of charm- and beauty-hadron production measured by LHCb are used together with inclusive and heavy-flavour production cross sections in deep inelastic scattering at HERA. The heavy-flavour data of the LHCb experiment impose additional constraints on the gluon and the sea-quark distributions at low partonic fractions
x
of the proton momentum, down to
x
∼
5
×
10
-
6
. This kinematic range is currently not covered by other experimental data in perturbative QCD fits.
HERAFitter Alekhin, S.; Behnke, O.; Belov, P. ...
The European physical journal. C, Particles and fields,
07/2015, Letnik:
75, Številka:
7
Journal Article
Recenzirano
Odprti dostop
HERAFitter is an open-source package that provides a framework for the determination of the parton distribution functions (PDFs) of the proton and for many different kinds of analyses in Quantum ...Chromodynamics (QCD). It encodes results from a wide range of experimental measurements in lepton–proton deep inelastic scattering and proton–proton (proton–antiproton) collisions at hadron colliders. These are complemented with a variety of theoretical options for calculating PDF-dependent cross section predictions corresponding to the measurements. The framework covers a large number of the existing methods and schemes used for PDF determination. The data and theoretical predictions are brought together through numerous methodological options for carrying out PDF fits and plotting tools to help to visualise the results. While primarily based on the approach of collinear factorisation, HERAFitter also provides facilities for fits of dipole models and transverse-momentum dependent PDFs. The package can be used to study the impact of new precise measurements from hadron colliders. This paper describes the general structure of HERAFitter and its wide choice of options.
Measurements of open charm and beauty production cross sections in deep inelastic
ep
scattering at HERA from the H1 and ZEUS Collaborations are combined. Reduced cross sections are obtained in the ...kinematic range of negative four-momentum transfer squared of the photon
2.5
GeV
2
≤
Q
2
≤
2000
GeV
2
and Bjorken scaling variable
3
·
10
-
5
≤
x
Bj
≤
5
·
10
-
2
. The combination method accounts for the correlations of the statistical and systematic uncertainties among the different datasets. Perturbative QCD calculations are compared to the combined data. A next-to-leading order QCD analysis is performed using these data together with the combined inclusive deep inelastic scattering cross sections from HERA. The running charm- and beauty-quark masses are determined as
m
c
(
m
c
)
=
1
.
290
-
0.041
+
0.046
(
exp
/
fit
)
-
0.014
+
0.062
(
model
)
-
0.031
+
0.003
(
parameterisation
)
GeV and
m
b
(
m
b
)
=
4
.
049
-
0.109
+
0.104
(
exp
/
fit
)
-
0.032
+
0.090
(
model
)
-
0.031
+
0.001
(
parameterisation
)
GeV
.
HERAFitter Alekhin, S; Behnke, O; Belov, P ...
The European physical journal. C, Particles and fields,
07/2015, Letnik:
75, Številka:
7
Journal Article
Recenzirano
Odprti dostop
HERAFitter is an open-source package that provides a framework for the determination of the parton distribution functions (PDFs) of the proton and for many different kinds of analyses in Quantum ...Chromodynamics (QCD). It encodes results from a wide range of experimental measurements in lepton-proton deep inelastic scattering and proton-proton (proton-antiproton) collisions at hadron colliders. These are complemented with a variety of theoretical options for calculating PDF-dependent cross section predictions corresponding to the measurements. The framework covers a large number of the existing methods and schemes used for PDF determination. The data and theoretical predictions are brought together through numerous methodological options for carrying out PDF fits and plotting tools to help to visualise the results. While primarily based on the approach of collinear factorisation, HERAFitter also provides facilities for fits of dipole models and transverse-momentum dependent PDFs. The package can be used to study the impact of new precise measurements from hadron colliders. This paper describes the general structure of HERAFitter and its wide choice of options.
The impact of recent measurements of heavy-flavour production in deep inelastic ep scattering and in pp collisions on parton distribution functions is studied in a QCD analysis in the fixed-flavour ...number scheme at next-to-leading order. Differential cross sections of charm- and beauty-hadron production measured by LHCb are used together with inclusive and heavy-flavour production cross sections in deep inelastic scattering at HERA. The heavy-flavour data of the LHCb experiment impose additional constraints on the gluon and the sea-quark distributions at low partonic fractions x of the proton momentum, down to Formula omitted. This kinematic range is currently not covered by other experimental data in perturbative QCD fits.
High-precision HERA data corresponding to a luminosity of around 1 fb−1 have been used in the framework of eeqq contact interactions (CI) to set limits on possible high-energy contributions beyond ...the Standard Model to electron-quark scattering. Measurements of the inclusive deep inelastic cross sections in neutral and charged current ep scattering were considered. The analysis of the ep data has been based on simultaneous fits of parton distribution functions including contributions of CI couplings to ep scattering. Several general CI models and scenarios with heavy leptoquarks were considered. Improvements in the description of the inclusive HERA data were obtained for a few models. Since a statistically significant deviation from the Standard Model cannot be established, limits in the TeV range were set on all models considered.
A
bstract
Two-particle azimuthal correlations have been measured in neutral current deep inelastic
ep
scattering with virtuality
Q
2
>
5 GeV
2
at a centre-of-mass energy
s
= 318 GeV recorded with the ...ZEUS detector at HERA. The correlations of charged particles have been measured in the range of laboratory pseudorapidity
−
1
.
5
< η <
2
.
0 and transverse momentum 0
.
1
< p
T
<
5
.
0 GeV and event multiplicities
N
ch
up to six times larger than the average 〈
N
ch
〉 ≈ 5. The two-particle correlations have been measured in terms of the angular observables
c
n
{2}
= 〈〈
cosn
Δ
φ
〉〉, where
n
is between 1 and 4 and ∆
φ
is the relative azimuthal angle between the two particles. Comparisons with available models of deep inelastic scattering, which are tuned to reproduce inclusive particle production, suggest that the measured two-particle correlations are dominated by contributions from multijet production. The correlations observed here do not indicate the kind of collective behaviour recently observed at the highest RHIC and LHC energies in high-multiplicity hadronic collisions.
A dual model with a nonlinear proton Regge trajectory in the missing mass (M_X^2) channel is constructed. A background based on a direct-channel exotic trajectory, developed and applied earlier for ...the inclusive electron-proton cross section description in the nucleon resonance region, is used. The parameters of the model are determined from the extrapolations to earlier experiments. Predictions for the low-mass (2 < M_X^2 < 8GeV^2) diffraction dissociation cross sections at the LHC energies are given.
At large values of x , the parton distribution functions (PDFs) of the proton are poorly constrained and there are considerable variations between different global fits. Data at such high x have ...already been published by the ZEUS Collaboration, but not yet used in PDF extractions. A technique for comparing predictions based on different PDF sets to the observed number of events in the ZEUS data is presented. It is applied to compare predictions from the most commonly used PDFs to published ZEUS data at high Bjorken x . A wide variation is found in the ability of the PDFs to predict the observed results. A scheme for including the ZEUS highx data in future PDF extractions is discussed.
PDF
