255 research outputs found
The H1 Forward Proton Spectrometer at HERA
The forward proton spectrometer is part of the H1 detector at the HERA
collider. Protons with energies above 500 GeV and polar angles below 1 mrad can
be detected by this spectrometer. The main detector components are
scintillating fiber detectors read out by position-sensitive photo-multipliers.
These detectors are housed in so-called Roman Pots which allow them to be moved
close to the circulating proton beam. Four Roman Pot stations are located at
distances between 60 m and 90 m from the interaction point.Comment: 20 pages, 10 figures, submitted to Nucl.Instr.and Method
Coherent Parton Showers with Local Recoils
We outline a new formalism for dipole-type parton showers which maintain
exact energy-momentum conservation at each step of the evolution. Particular
emphasis is put on the coherence properties, the level at which recoil effects
do enter and the role of transverse momentum generation from initial state
radiation. The formulated algorithm is shown to correctly incorporate coherence
for soft gluon radiation. Furthermore, it is well suited for easing matching to
next-to-leading order calculations.Comment: 24 pages, 3 figure
Performance for proton anisotropic flow measurement of the CBM experiment at FAIR
The Compressed Baryonic Matter experiment (CBM) performance for proton anisotropic flow measurements is studied with Monte-Carlo simulations using collisions of gold ions at lab momentum of 12A GeV/c employing DCM-QGSM-SMM heavy-ion event generator. Realistic procedures are used for centrality estimation with the number of registered tracks and particle identification with information from Time-Of-Flight detector. Variation of directed flow estimates depending on various combinations of PSD modules is used to evaluate possible systematic biases due to collision symmetry plane estimation
Using multiplicity of produced particles for centrality determination in heavy-ion collisions with the CBM experiment
The evolution of matter created in a heavy-ion collision depends on its initial geometry. Experimentally collision geometry is characterized with centrality. Procedure of centrality determination for the Compressed Baryonic Matter (CBM) experiment at FAIR is presented. Relation between parameters of the collision geometry (such as impact parameter magnitude) and centrality classes is extracted using multiplicity of produced charged particles. The latter is connected to the collision geometry parameters using Monte-Carlo Glauber approach
Herwig++ Status Report
Herwig++ is the successor of the event generator HERWIG. In its present version 2.2.1 it provides a program for full LHC event generation which is superior to the previous program in many respects. We briefly summarize its features and describe present work and some future plans
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Challenges in QCD matter physics --The scientific programme of the Compressed Baryonic Matter experiment at FAIR
Substantial experimental and theoretical efforts worldwide are devoted to explore the phase diagram of strongly interacting matter. At LHC and top RHIC energies, QCD matter is studied at very high temperatures and nearly vanishing net-baryon densities. There is evidence that a Quark-Gluon-Plasma (QGP) was created at experiments at RHIC and LHC. The transition from the QGP back to the hadron gas is found to be a smooth cross over. For larger net-baryon densities and lower temperatures, it is expected that the QCD phase diagram exhibits a rich structure, such as a first-order phase transition between hadronic and partonic matter which terminates in a critical point, or exotic phases like quarkyonic matter. The discovery of these landmarks would be a breakthrough in our understanding of the strong interaction and is therefore in the focus of various high-energy heavy-ion research programs. The Compressed Baryonic Matter (CBM) experiment at FAIR will play a unique role in the exploration of the QCD phase diagram in the region of high net-baryon densities, because it is designed to run at unprecedented interaction rates. High-rate operation is the key prerequisite for high-precision measurements of multi-differential observables and of rare diagnostic probes which are sensitive to the dense phase of the nuclear fireball. The goal of the CBM experiment at SIS100 (sNN= 2.7--4.9 GeV) is to discover fundamental properties of QCD matter: the phase structure at large baryon-chemical potentials (μB> 500 MeV), effects of chiral symmetry, and the equation of state at high density as it is expected to occur in the core of neutron stars. In this article, we review the motivation for and the physics programme of CBM, including activities before the start of data taking in 2024, in the context of the worldwide efforts to explore high-density QCD matter
SUSY parameter determination at the LHC using cross sections and kinematic edges
We study the determination of supersymmetric parameters at the LHC from a
global fit including cross sections and edges of kinematic distributions. For
illustration, we focus on a minimal supergravity scenario and discuss how well
it can be constrained at the LHC operating at 7 and 14 TeV collision energy,
respectively. We find that the inclusion of cross sections greatly improves the
accuracy of the SUSY parameter determination, and allows to reliably extract
model parameters even in the initial phase of LHC data taking with 7 TeV
collision energy and 1/fb integrated luminosity. Moreover, cross section
information may be essential to study more general scenarios, such as those
with non-universal gaugino masses, and distinguish them from minimal,
universal, models.Comment: 22 pages, 8 figure
The very forward hadron calorimeter PSD for the future CBM@FAIR experiment
The Projectile Spectator Detector (PSD) of the CBM experiment at the future FAIR facility is a compensating lead-scintillator calorimeter designed to measure the energy distribution of the forward going projectile nucleons and nuclei fragments (reaction spectators) produced close to the beam rapidity. The detector performance for the centrality and reaction plane determination is re- viewed based on Monte-Carlo simulations of gold-gold collisions by means of four different heavy-ion event generators. The PSD energy resolution and the linearity of the response measured at CERN PS for the PSD supermodule consisting of 9 modules are presented. Predictions of the calorimeter radiation conditions at CBM and response measurement of one PSD module equipped with neutron irradiated MPPCs used for the light read out are discussed
Challenges in QCD matter physics - The Compressed Baryonic Matter experiment at FAIR
Substantial experimental and theoretical efforts worldwide are devoted to
explore the phase diagram of strongly interacting matter. At LHC and top RHIC
energies, QCD matter is studied at very high temperatures and nearly vanishing
net-baryon densities. There is evidence that a Quark-Gluon-Plasma (QGP) was
created at experiments at RHIC and LHC. The transition from the QGP back to the
hadron gas is found to be a smooth cross over. For larger net-baryon densities
and lower temperatures, it is expected that the QCD phase diagram exhibits a
rich structure, such as a first-order phase transition between hadronic and
partonic matter which terminates in a critical point, or exotic phases like
quarkyonic matter. The discovery of these landmarks would be a breakthrough in
our understanding of the strong interaction and is therefore in the focus of
various high-energy heavy-ion research programs. The Compressed Baryonic Matter
(CBM) experiment at FAIR will play a unique role in the exploration of the QCD
phase diagram in the region of high net-baryon densities, because it is
designed to run at unprecedented interaction rates. High-rate operation is the
key prerequisite for high-precision measurements of multi-differential
observables and of rare diagnostic probes which are sensitive to the dense
phase of the nuclear fireball. The goal of the CBM experiment at SIS100
(sqrt(s_NN) = 2.7 - 4.9 GeV) is to discover fundamental properties of QCD
matter: the phase structure at large baryon-chemical potentials (mu_B > 500
MeV), effects of chiral symmetry, and the equation-of-state at high density as
it is expected to occur in the core of neutron stars. In this article, we
review the motivation for and the physics programme of CBM, including
activities before the start of data taking in 2022, in the context of the
worldwide efforts to explore high-density QCD matter.Comment: 15 pages, 11 figures. Published in European Physical Journal
Measurement of D* Meson Cross Sections at HERA and Determination of the Gluon Density in the Proton using NLO QCD
With the H1 detector at the ep collider HERA, D* meson production cross
sections have been measured in deep inelastic scattering with four-momentum
transfers Q^2>2 GeV2 and in photoproduction at energies around W(gamma p)~ 88
GeV and 194 GeV. Next-to-Leading Order QCD calculations are found to describe
the differential cross sections within theoretical and experimental
uncertainties. Using these calculations, the NLO gluon momentum distribution in
the proton, x_g g(x_g), has been extracted in the momentum fraction range
7.5x10^{-4}< x_g <4x10^{-2} at average scales mu^2 =25 to 50 GeV2. The gluon
momentum fraction x_g has been obtained from the measured kinematics of the
scattered electron and the D* meson in the final state. The results compare
well with the gluon distribution obtained from the analysis of scaling
violations of the proton structure function F_2.Comment: 27 pages, 9 figures, 2 tables, submitted to Nucl. Phys.
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