We discuss the physics of large impact parameter interactions at the LHC: ultraperipheral collisions (UPCs). The dominant processes in UPCs are photon–nucleon (nucleus) interactions. The current LHC ...detector configurations can explore hard phenomena at small
x
with nuclei and nucleons at photon–nucleon center-of-mass energies above 1 TeV, extending the
x
range of HERA by a factor of ten. In particular, it will be possible to probe diffractive and inclusive parton densities in nuclei using several processes. The interaction of small dipoles with protons and nuclei can be investigated in elastic and quasi-elastic
J
/
ψ
and
Υ
production as well as in high
t
ρ
0
production accompanied by a rapidity gap. Several of these phenomena provide clean signatures of the onset of the new high gluon density QCD regime. The LHC is in the kinematic range where nonlinear effects are several times larger than those at HERA. Two-photon processes in UPCs are also studied. In addition, while UPCs play a role in limiting the maximum beam luminosity, they can also be used as a luminosity monitor by measuring mutual electromagnetic dissociation of the beam nuclei. We also review similar studies at HERA and RHIC as well as describe the potential use of the LHC detectors for UPC measurements.
This paper will discuss the performance of the PHOS level-0 trigger and planned improvements for RUN 2. Due to hardware constraints the Trigger Region Unit boards are limited to an operating ...frequency of 20 MHz. This has led to some ambiguity and biases of the trigger inputs. The trigger input generation scheme was therefore optimized to improve the performance. The PHOS level-0 trigger system has been working with an acceptable efficiency and purity. Proposed actions to further improve the performance and possibly eliminate the impact of the biased trigger inputs will also be presented.
We present the two electromagnetic calorimeters of the ALICE (A Large Ion Collider Experiment) experiment at LHC (Large Hadron Collider). One is the high-resolution PHOton Spectrometer (PHOS) made of ...lead tungsten crystals and the other is the ElectroMagnetic Calorimeter (EMCal), a Lead-Scintillator sampling calorimeter. They are dedicated to the measurement and identification of direct photons, light neutral mesons such as
π
0
,
η and
ω
(
782
)
, and jets emitted in proton-proton and heavy-ion collisions at the LHC energies. The PHOS is capable of precisely detecting photons with momentum range between 0.1 GeV/c and 100 GeV/c and the EMCal can extend the prompt photon and light neutral meson momentum measurement beyond 200 GeV/c. The objective of the study is to explore the physics of strongly interacting QCD matter under extreme conditions of energy density.
High pt and photon physics with ALICE at LHC 周代翠 万仁卓 毛亚显 Y. Schutz 王梦亮 马科 王亚平 殷中宝 蔡勖 Y. Kharlov G. Conesa C. Roy
Chinese physics C,
09/2010, Letnik:
34, Številka:
9
Journal Article
Recenzirano
ALICE,A Large Ion Collider Experiment,is dedicated to study the QCD matter at extreme high temperature and density to understand the Quark Gluon Plasma （QGP） and phase ...transition.High-transversemomentum photons and neutral mesons from the initial hard scattering of partons can be measured with ALICE calorimeters,PHOS （PHOton Spectrometer） and EMCAL （ElectroMagnetic CALorimeter）.Combing the additional central tracking detectors,the γ-jet and π 0-jet measurements thus can be accessed.These measurements offer us a sensitive tomography probe of the hot-dense medium generated in the heavy ion collisions.In this paper,high p T and photon physics is discussed and the ALICE calorimeters capabilities of high-transverse-momentum neutral mesons and γ-jet measurements are presented.
Performance of the ALICE photon spectrometer PHOS Conesa, G.; Delagrange, H.; Díaz, J. ...
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment,
01/2005, Letnik:
537, Številka:
1-2
Journal Article, Conference Proceeding
Recenzirano
We present in this paper the measured characteristics of a 64 lead–tungstate crystal array designed to detect high-energy photons and neutral mesons with the ALICE photon spectrometer PHOS. The array ...has been tested with electron and charged pion secondary beams delivered by the CERN PS and SPS synchrotrons. Photon energy and π0 invariant mass resolutions are presented. The PHOS particle identification performance for data simulated with the AliRoot package is studied.
Identification of photon-tagged jets in the ALICE experiment Conesa, G.; Delagrange, H.; Díaz, J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
2008, Letnik:
585, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The ALICE experiment at LHC will detect and identify prompt photons and light neutral-mesons with the PHOS detector and the additional EMCal electromagnetic calorimeter. Charged particles will be ...detected and identified by the central tracking system. In this article, the possibility of studying the interaction of jets with the nuclear medium, using prompt photons as a tool to tag jets, is investigated by simulations. New methods to identify prompt photon-jet events and to distinguish them from the jet–jet background are presented.
The ALICE experiment at LHC will detect and identify prompt photons and light neutral mesons with the PHOS and EMCal detectors. Charged particles will be detected and identified by the central ...tracking system. In this paper, a method to identify prompt photons and to separate them from the background of hadrons and decay photons in PHOS with the help of isolation cuts is presented.
The Shashlyk calorimeter prototype for the PANDA experiment has been constructed at IHEP and experimentally tested using the 1-19 GeV electron beam with high precision momentum tagging at the IHEP ...accelerator. Results of the first measurements for the fine-segmented Shashlyk calorimeter prototype in the wide energy range up to 19 GeV are presented. Fair energy and position resolutions having been obtained are in a good agreement with the Monte-Carlo simulations. Detection inefficiency due to holes for straight light fibers has turned out to be negligible for PANDA. Plans for the near term future including approaching test beam study of π0 reconstruction capability of shashlyk prototype are also discussed.
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