共查询到20条相似文献,搜索用时 515 毫秒
1.
J. Mercado 《Physics of Particles and Nuclei Letters》2011,8(9):885-887
ALICE is the experiment at the CERN Large Hadron Collider dedicated to study high-energy nuclear collisions which is also
carrying out a proton-proton physics program, thanks to its wide phase-space coverage and good momentum and spatial resolution.
We present first results on two-pion Bose-Einstein correlations in pp collisions at √s = 900 GeV measured with ALICE. An increase of the HBT radius with increasing event multiplicity is observed, in agreement
with previous measurements. However, a strong decrease of the radius with increasing transverse momentum, as observed at RHIC
and at Tevatron, is not evident in our analysis. 相似文献
2.
Kohei Fujiwara 《Czechoslovak Journal of Physics》2005,55(12):1639-1643
The PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) is being upgraded with a novel four-layer silicon vertex
tracker. The detector will enhance the physics capabilities of PHENIX in the future phase of the heavy-ion and the polarized
proton-proton programs at RHIC. The silicon vertex tracker will allow the direct measurement of heavy quark production by
identifying displaced decay vertices, and will reconstruct jets with nearly full azimuthal coverage over |η| < 1.2. We are
developing a novel Silicon Pixel Detector for the inner two barrel layers of the silicon vertex tracker. In this paper, the
status of the development is reported.
for the PHENIX collaboration
Presented in the Poster Session “Future Experiments and Facilities” at the 18th International Conference “Quark Matter 2005”,
Budapest, Hungary, 4–9 August 2005. 相似文献
3.
J. W. Harris 《The European Physical Journal C - Particles and Fields》2005,43(1-4):445-450
Potential near- and long-term physics opportunities with jets, heavy flavors and electromagnetic probes at RHIC are presented. Much new physics remains to be unveiled using these probes, due to their sensitivity to the initial high density stage of RHIC collisions, when quark-gluon plasma (QGP) formation is expected. Additional physics will include addressing deconfinement, chiral symmetry restoration, properties of the strongly-coupled QGP and a possible weakly-interacting QGP, color glass condensate in the initial state, and hadronization. To fully realize the physics prospects of the RHIC energy regime, new detector components must be added to existing experiments, the RHIC machine luminosity upgraded, and a possible new detector with significantly extended coverage and capabilities added.Arrival of the final proofs: 26 July 2005PACS:
25.75Nq 相似文献
4.
G. Renault B. S. Nielsen J. Westergaard J. J. Gaardhoje 《Czechoslovak Journal of Physics》2005,55(12):1671-1674
A Large Ion Collider Experiment (ALICE) is the only experiment at the Large Hadron Collider (LHC) dedicated to the study of
heavy ion collisions. The Time Projection Chamber (TPC) is the main tracking detector covering the pseudo rapidity range |η|
< 0.9. It is designed for a maximum multiplicity dN/dy = 8000. The aim of the laser system is to simulate ionizing tracks at predifined positions throughout the drift volume in
order to monitor the TPC response to a known source. In particular, the alignment of the read-out chambers will be performed,
and variations of the drift velocity due to drift field imperfections can be measured and used as calibration data in the
physics data analysis. In this paper we present the design of the pulsed UV laser and optical system, together with the control
and monitoring systems.
for the ALICE Collaboration
Presented in the Poster Session “Future Experiments and Facilities” at the 18th International Conference “Quark Matter 2005”,
Budapest, Hungary, 4–9 August 2005. 相似文献
5.
Sevil Salur 《The European Physical Journal C - Particles and Fields》2009,62(1):119-125
Jets can be used to probe the physical properties of the high energy density matter created in collisions at the Relativistic
Heavy Ion Collider (RHIC). Measurements of strong suppression of inclusive hadron distributions and di-hadron correlations
at high p
T
have already provided evidence for partonic energy loss. However, these measurements suffer from well-known geometric biases
due to the competition of energy loss and fragmentation. These biases can be avoided if the jets are reconstructed independently
of their fragmentation details—quenched or unquenched. In this paper, we discuss modern jet reconstruction algorithms (cone
and sequential recombination) and their corresponding background subtraction techniques required by the high multiplicities
of heavy ion collisions. We review recent results from the STAR experiment at RHIC on direct jet reconstruction in central
Au+Au collisions at
GeV. 相似文献
6.
A. Zelenski G. Atoian J. Ritter D. Steski F. Podolyako I. Sorokin I. Vizgalov V. Klenov V. Zubets V. Davydenko A. Ivanov A. Kolmogorov 《Physics of Particles and Nuclei》2014,45(1):308-311
The RHIC polarized H? ion source is being upgraded to higher intensity and polarization for use in the RHIC polarization physics program at enhanced luminosity RHIC operation. The higher beam intensity will allow reduction of the longitudinal transverse beam emittance at injection to AGS to reduce polarization losses in AGS. There is also a planned RHIC luminosity upgrade by using the electron beam lens to compensate the beam-beam interaction at collision points. This upgrade is also essential for future BNL plans for a high-luminosity electron-proton (ion) Collider eRHIC. The basic limitations on the high-intensity H? ion beam production in charge-exchange collisions of the neutral atomic hydrogen beam in the Na-vapor jet ionizer cell were experimentally studied. 相似文献
7.
A. Dainese 《The European Physical Journal C - Particles and Fields》2007,49(1):135-141
At LHC energy, heavy quarks will be abundantly produced and the design of the ALICE detector will allow us to study their
production using several channels. The expected heavy-quark in-medium energy loss in nucleus-nucleus collisions at the LHC
is calculated within a model, that is compared to the available heavy-quark quenching measurements at RHIC. The nuclear modification
factors and heavy-to-light ratios of charm and beauty mesons are considered. The capability of the ALICE experiment for addressing
this phenomenology is discussed.
PACS 25.75.-q; 14.65.Dw; 13.25.Ft 相似文献
8.
ALICE (A Large Ion Collider Experiment) is the LHC detector designed to measure nucleus-nucleus (AA) collisions where the formation of the Quark Gluon Plasma is expected. The experiment will also study proton-proton (pp) collisions at 14 TeV. Amongst the relevant observables to be investigated in pp collisions, the B-hadron cross-section is particularly interesting since it provides benchmarks for theoretical models and it is mandatory
for understanding heavy flavour production in AA collisions. The performances of the ALICE muon spectrometer to measure B-hadron cross-section in pp collisions at 14 TeV via single muons are presented. 相似文献
9.
The large hadron collider (LHC) under construction at CERN will deliver ion beams up to centre of mass energies of the order
of 5.5 TeV per nucleon, in case of lead. If compared to the available facilities for the study of nucleus-nucleus collisions
(SpS and RHIC), this represents a huge step forward in terms of both volume and energy density that can be attained in nuclear
interactions. ALICE (a large ion collider experiment) is the only detector specifically designed for the physics of nuclear
collisions at LHC, even though it can also study high cross-section processes occurring in proton-proton collisions. The main
goal of the experiment is to observe and study the phase transition from hadronic matter to deconfined partonic matter (quark
gluon plasma —QGP). ALICE is conceived as a general-purpose detector and will address most of the phenomena related to the
QGP formation at LHC energies: for this purpose, a large fraction of the hadrons, leptons and photons produced in each interaction
will be measured and identified. 相似文献
10.
The study of very high transverse-momentum jets will be an important issue at the LHC, in particular since the corresponding
cross sections will be considerably larger than at RHIC energies. Jets are expected to provide information on QGP formation,
due to the energy loss of fast partons in the medium. Jet cross sections can in principle be compared to simple pQCD calculations,
based on the hypothesis of factorization. But often it is useful or even necessary to not only compute the production rate
of the very high-p
T jets, but in addition the “rest of the event”. The proposed talk is based on recent work, where we try to construct an event
generator—fully compatible with pQCD—which allows one to compute complete events, consisting of high-p
T jets plus all the other low p
T particles produced at the same time. Whereas in “generators of inclusive spectra” like Pythia one may easily trigger on high-p
T phenomena, this is not so obvious for “generators of physical events”, where in principle one has to generate a very large
number of events in order to finally obtain rare events (like those with a very high-p
T jet). We shall discuss how we overcome these difficulties in the framework of the EPOS model. 相似文献
11.
The Large Hadron Collider (LHC) under construction at CERN is also planned as a heavy ion collider with lead ions colliding at an energy of 2.7+2.7 ATeV. This corresponds to collisions of matter with cosmic rays of the utmost energies observed so far promising the study of new and exciting aspects of physics. Minor improvements of the newly commissioned lead ion source at the CERN SPS are necessary in order to provide a luminosity of L=2×1027 cm?2s?1. The detector ALICE has been chosen as the third detector for the LHC and will be dedicated to the physics of these nuclear collisions and also to the large cross section physics in p+p collisions. 相似文献
12.
The possibility of measuring cross sections for the production of J/ψ mesons in fixed-target experiments with the proton and ion beams of the Large Hadron Collider (LHC) at CERN (Switzerland)
is considered. At the present time, measurements of charmonium production in proton-proton collisions at an energy of 7 TeV
have begun at LHC. Previously, the production of J/ψ and ψ′ mesons was studied in the NA38, NA50, and NA60 fixed-target experiments with beams of the CERN synchrotron (SPS) and in the
PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC, Brookhaven National Laboratory, USA). A normal nuclear absorption
of J/ψ mesons in proton-nucleus collisions and an enhanced, anomalous, suppression of the production of charmonium states in central
collisions of relativistic nuclei were observed. At the present time, there are no theoretical models that could describe
the entire body of experimental data. Measurements over a broad interval of proton and ion energies are required. Measurements
of charmonium production using LHC beams with fixed targets in the energy range between the SPS and RHIC energies-a beam of
7-TeV protons (√s = 114.6 GeV) and a beam of 2.75-TeV/nucleon lead ions (√s = 71.8 GeV)-will provide an additional possibility for studying the charmonium-production mechanism. Estimates of the geometric
acceptance, luminosity, and counting rate for the production of J/ψ mesons are presented. 相似文献
13.
P. Chiappetta P. Colangelo J. -Ph. Guillet G. Nardulli 《Zeitschrift fur Physik C Particles and Fields》1993,59(4):629-639
We perform a systematic analysis of different processes with high energy polarized proton beams: jets, direct photon, lepton pairs (Drell-Yan) andWZ production. Different sets of polarized partonic densities are used that fit EMC and SLAC polarized deep inelastic scattering data with variable amount of quark and gluon components of the proton spin. The case of the future Relativistic Heavy Ion Collider (RHIC) used as a polarized collider at a maximum energy of \(\sqrt s = 500\) GeV is analyzed in detail. 相似文献
14.
Sergey Petrushanko 《The European Physical Journal C - Particles and Fields》2009,61(4):665-674
The measurement of the charmonium and bottomonium resonances in nucleus-nucleus collisions provides crucial information on
high-density QCD matter. First, the suppression of quarkonia production is generally agreed to be one of the most direct probes
of quark-gluon plasma formation. The observation of anomalous J/ψ suppression at the CERN-SPS and at RHIC is well established but the clarification of some important remaining questions requires
equivalent studies of the ϒ family, will be possible at the LHC. Second, the production of heavy-quarks proceeds mainly via gluon-gluon fusion processes
and, as such, is sensitive to saturation of the gluon density at low-x in the nucleus. Measured departures from the expected vacuum quarkonia cross-sections in Pb+Pb collisions at the LHC will
thus provide valuable information not only on the thermodynamical state of the produced partonic medium, but also on the initial-state
modifications of the nuclear parton distribution functions. The capabilities of the LHC detectors (ALICE, ATLAS and CMS) to
study quarkonia production in Pb+Pb collisions at 5.5 TeV per nucleon pair are discussed. 相似文献
15.
F. Guérin 《The European Physical Journal C - Particles and Fields》2007,49(1):143-148
ALICE (A Large Ion Collider Experiment) is the LHC detector dedicated to the study of nucleus–nucleus collisions, in which
the formation of the quark–gluon plasma (QGP) is expected. Heavy quarkonia, especially the Upsilon states, are relevant for
studying the QGP since they provide an essential probe of the earliest and hottest stages of heavy ion collisions. They will
be measured via their dimuon decay channel in ALICE in the muon spectrometer. The muon spectrometer performance has been studied
in simulations, the results will be presented with emphasis on the trigger efficiency and rate in Pb–Pb collisions. The expected
yields of Upsilon states will be extracted from a simulation based on a global fit of the dimuon mass spectra for different
collision centralities. 相似文献
16.
The possibilities to determine the flavor structure of the polarized sea (antiquark) distributions of the nucleon via vector
boson production at high energy polarized hadron–hadron colliders, such as the Relativistic Heavy–Ion Collider (RHIC), are studied
in detail. In particular the perturbative stability of the expected asymmetries in two representative models for the (un)broken
flavor structure are investigated by confronting perturbative QCD leading order predictions of the expected asymmetries with
their next–to–leading order counterparts.
Received: 28 November 2000 / Published online: 5 February 2001 相似文献
17.
Yousef Makdisi 《Physics of Particles and Nuclei》2014,45(1):268-269
The Relativistic Heavy Ions Collider (RHIC) has accelerated polarized proton beams for physics since 2001. As part of the future eRHIC program and in order to enhance access to the down quark, a program to accelerate polarized 3He in the AGS and RHIC is envisioned. To that end, a polarized 3He source is being built at MIT. This will be installed on the BNL EBIS source in preparation for injection into the booster and AGS. As an early exercise, in June 2012, unpolarized 3He beams have been accelerated in the AGS. This paper will peruse some potential ideas for 3He polarimetry and calibration that could be utilized at the AGS as well as RHIC. The current proton polarimetry program serves as a guide. 相似文献
18.
V. S. Pantuev 《Physics of Atomic Nuclei》2009,72(12):1971-1981
The most recent physics results obtained at the Relativistic Heavy Ion Collider (RHIC) are surveyed. The survey is devoted
to considering p + p, Cu + Cu, and Au + Au systems of colliding nuclei at c.m. energies of √
s
NN = 200, 62.4, and 22.4 GeV. The results obtained within the first years of collider operation are discussed. New data on the
production of high-transverse-momentum particles are presented. Manifestations of collective flows, such as the radial and
elliptic flows, as well as the formation of a shock wave and a ridge, are considered. The results concerning heavy-quark production
are also discussed. 相似文献
19.
G. J. Kunde H. van Hecke K. Hessler C. Mironov 《The European Physical Journal C - Particles and Fields》2009,61(4):785-788
The Large Hadron Collider will allow studies of hard probes in nucleus-nucleus collisions which were not accessible at the
Relativistic Heavy Ion Collider—even the study of small cross-section Z
0-tagged jets becomes possible. Going beyond the measurement of back-to-back correlations of two strongly interacting particles
to measure plasma properties, we replace one side by an electromagnetic probe which propagates through the plasma undisturbed
and therefore provides a measurement of the energy of the initial hard scattering. We show that at sufficiently high transverse
momentum the Z
0-tagged jets originate predominately from the fragmentation of quarks and anti-quarks while gluon jets are suppressed. We
propose to use lepton-pair tagged jets to study medium-induced partonic energy loss and to measure in-medium parton fragmentation
functions to determine the opacity of the quark gluon plasma. 相似文献
20.
This review of low-p
T proton-proton physics at low luminosity at the large hadron collider (LHC) should cover all LHC experiments, but in practice,
is mainly related to ALICE, for reasons which will be explained. However, the relevance to other LHC experiments is clear,
as low-pT. phenomena represent an important component of the background to their high-pT. phenomena which needs to be calibrated. The ALICE collaboration will study proton-proton collisions as part of their heavy-ion
programme, where most signals are relative to the proton-proton system. In addition, the ALICE detector’s unique acceptance
at low pT as well as its unique particle identification capability will make it possible to carry out a program of genuine proton-proton
physics complementary to those of other LHC experiments. 相似文献