A
bstract
We present a state-of-the-art computation for the production of dijets in proton-proton and proton-lead collisions at the LHC, in forward rapidity domains covered by the ATLAS calorimeter ...and the planned FoCal extension of the ALICE detector. We use the small-
x
improved TMD (ITMD) formalism, together with collinearly improved TMD gluon distributions and full
b
-space Sudakov resummation, and discuss nonperturbative corrections due to hadronization and showers using the Pythia event generator. We observe that the production of forward dijets in proton-nucleus collisions at moderately low
p
T
is an excellent probe of saturation effects, and demonstrate that the Sudakov resummation does not alter the suppression of the cross section.
We study 3-jet event topologies in proton-proton collisions at a centre-of-mass energy of
s
=
13
TeV
in a configuration, where one jet is present in the central pseudorapidity region (
|
η
|
<
2.0
) ...while two other jets are in a more forward (same hemisphere) area (
|
η
|
>
2.0
). We compare various parton level predictions using: collinear factorisation,
k
T
-factorisation with fully off-shell matrix elements and the hybrid framework. We study the influence of different parton distribution functions, initial state radiation, final state radiation, and hadronisation. We focus on differential cross sections as a function of azimuthal angle difference between the leading dijet system and the third jet, which is found to have excellent sensitivity to the physical effects under study.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
LHC forward physics Akiba, K; Baillie, O Villalobos; Baus, C ...
Journal of physics. G, Nuclear and particle physics,
2016, Letnik:
43, Številka:
11
Journal Article
Recenzirano
Odprti dostop
The goal of this report is to give a comprehensive overview of the rich field of forward physics, with a special attention to the topics that can be studied at the LHC. The report starts presenting a ...selection of the Monte Carlo simulation tools currently available, chapter 2, then enters the rich phenomenology of QCD at low, chapter 3, and high, chapter 4, momentum transfer, while the unique scattering conditions of central exclusive production are analyzed in chapter 5. The last two experimental topics, Cosmic Ray and Heavy Ion physics are presented in the chapter 6 and 7 respectively. Chapter 8 is dedicated to the BFKL dynamics, multiparton interactions, and saturation. Here, the report ends with an overview of the forward detectors at LHC. Each chapter is correlated with a comprehensive bibliography, attempting to provide to the interested reader with a wide opportunity for further studies.
Charged particle multiplicity distributions in positron-proton deep inelastic scattering at a centre-of-mass energy Formula omitted GeV are measured. The data are collected with the H1 detector at ...HERA corresponding to an integrated luminosity of 136 pb Formula omitted. Charged particle multiplicities are measured as a function of photon virtuality Formula omitted, inelasticity y and pseudorapidity Formula omitted in the laboratory and the hadronic centre-of-mass frames. Predictions from different Monte Carlo models are compared to the data. The first and second moments of the multiplicity distributions are determined and the KNO scaling behaviour is investigated. The multiplicity distributions as a function of Formula omitted and the Bjorken variable Formula omitted are converted to the hadron entropy Formula omitted, and predictions from a quantum entanglement model are tested.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The azimuthal correlation,
Δ
ϕ
12
, of high transverse momentum jets in pp collisions at
s
=
13
TeV is studied by applying PB-TMD distributions to NLO calculations via MCatNLO together with the ...PB-TMD parton shower. A very good description of the cross section as a function of
Δ
ϕ
12
is observed. In the back-to-back region of
Δ
ϕ
12
→
π
, a very good agreement is observed with the PB-TMD Set 2 distributions while significant deviations are obtained with the PB-TMD Set 1 distributions. Set 1 uses the evolution scale while Set 2 uses transverse momentum as an argument in
α
s
, and the above observation therefore confirms the importance of an appropriate soft-gluon coupling in angular ordered parton evolution. The total uncertainties of the predictions are dominated by the scale uncertainties of the matrix element, while the uncertainties coming from the PB-TMDs and the corresponding PB-TMD shower are very small. The
Δ
ϕ
12
measurements are also compared with predictions using MCatNLO together
Pythia
8, illustrating the importance of details of the parton shower evolution.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The production of leading neutrons, where the neutron carries a large fraction
x
L
of the incoming proton’s longitudinal momentum, is studied in deep-inelastic positron-proton scattering at HERA. The ...data were taken with the H1 detector in the years 2006 and 2007 and correspond to an integrated luminosity of 122 pb
−1
. The semi-inclusive cross section is measured in the phase space defined by the photon virtuality 6<
Q
2
<100 GeV
2
, Bjorken scaling variable 1.5⋅10
−4
<
x
<3⋅10
−2
, longitudinal momentum fraction 0.32<
x
L
<0.95 and neutron transverse momentum
p
T
<0.2 GeV. The leading neutron structure function,
, and the fraction of deep-inelastic scattering events containing a leading neutron are studied as a function of
Q
2
,
x
and
x
L
. Assuming that the pion exchange mechanism dominates leading neutron production, the data provide constraints on the shape of the pion structure function.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The H1 very forward proton spectrometer at HERA Astvatsatourov, A.; Cerny, K.; Delvax, J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2014, Letnik:
736
Journal Article
Recenzirano
The very forward proton spectrometer, VFPS, is a component of the H1 detector at the HERA collider. Scattered protons emitted with a polar angle less than 1mrad and carrying a fractional energy 1−xP, ...0.008<xP≤0.028 of the incident proton beam energy can be detected by scintillating fiber detectors which are read out by position sensitive photo-multipliers. These detectors are contained in Roman pot stations which are moved close to the circulating proton beam. The structure, operation and performance of the two Roman pot stations located at about 220m from the H1 interaction point in the cryogenic section of the proton ring are described.
We study the light output, light collection efficiency and signal timing of a variety of organic scintillators that are being considered for the upgrade of the hadronic calorimeter of the CMS ...detector. The experimental data are collected at the H2 test-beam area at CERN, using a 150 GeV muon beam. In particular, we investigate the usage of over-doped and green-emitting plastic scintillators, two solutions that have not been extensively considered. We present a study of the energy distribution in plastic-scintillator tiles, the hit efficiency as a function of the hit position, and a study of the signal timing for blue and green scintillators.
We present performance studies of a full-length prototype for the CASTOR quartz-tungsten sampling calorimeter, installed in the very forward region of the CMS experiment at the LHC. The response ...linearity and energy resolution, the uniformity, as well as the showers’ spatial properties in the prototype have been studied with electrons, pions and muons of various energies. A special study was also carried out for testing the light-output with a 90-degree cut of the quartz plates of the calorimeter. The data were taken during the CASTOR test beam at CERN/SPS in 2007.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The Phase I upgrade of the CMS Hadron Endcap Calorimeters consists of new photodetectors (Silicon Photomultipliers in place of Hybrid Photo-Diodes) and front-end electronics. The upgrade will ...eliminate the noise and the calibration drift of the Hybrid Photo-Diodes and enable the mitigation of the radiation damage of the scintillators and the wavelength shifting fibers with a larger spectral acceptance of the Silicon Photomultipliers. The upgrade also includes increased longitudinal segmentation of the calorimeter readout, which allows pile-up mitigation and recalibration due to depth-dependent radiation damage. As a realistic operational test, the responses of the Hadron Endcap Calorimeter wedges were calibrated with a 60Co radioactive source with upgrade electronics. The test successfully established the procedure for future source calibrations of the Hadron Endcap Calorimeters. Here we describe the instrumentation details and the operational experiences related to the sourcing test.