4,322 research outputs found
Soft probes of high density QCD physics with CMS
The CMS heavy-ion program will probe QCD matter under extreme conditions. Its
capabilities for the study of global observables and soft probes are described.Comment: 6 pages, 10 figures. Presented at the International Conference on
Strangeness in Quark Matter 2007, Levoca, Slovakia, 28 June 200
Large Angle Hadron Correlations from Medium-Induced Gluon Radiation
Final state medium-induced gluon radiation in ultradense nuclear matter is
examined and shown to favor large angle emission when compared to vacuum
bremsstrahlung due to the suppression of collinear gluons. Perturbative
expression for the contribution of its hadronic fragments to the back-to-back
particle correlations is derived. It is found that in the limit of large jet
energy loss gluon radiation determines the yield and angular distribution of |
Delta phi | > Pi/2 di-hadrons to transverse momenta pT2 of the associated
particles. Clear transition from enhancement to suppression of the away-side
hadron correlations is established at moderate pT2 and its experimentally
accessible features are predicted versus the trigger particle momentum pT1.Comment: 5 pages, 3 figures. Figures 1 and 2 and some of the text revised.
Footnote added. As published in Phys. Lett.
High pT leading hadron suppression in nuclear collisions at sqrt(s_NN) = 20 -- 200 GeV: data versus parton energy loss models
Experimental results on high transverse momentum (leading) hadron spectra in
nucleus-nucleus collisions in the range sqrt(s_NN) = 20 -- 200 GeV are reviewed
with an emphasis on the observed suppression compared to free space production
in proton-proton collisions at the corresponding center-of-mass energies. The
transverse-momentum and collision-energy (but seemingly not the in-medium path
length) dependence of the experimental suppression factors measured in central
collisions is consistent with the expectations of final-state non-Abelian
parton energy loss in a dense QCD medium.Comment: Two typos correcte
Exclusive Photoproduction of and lepton pairs in Pb-Pb at 5.5 TeV
Electromagnetic interactions of heavy-ions give access to a unique programme of photon-induced studies in the QCD and QED sectors of the Standard Model. On the one hand, exclusive photoproduction of bottomonium (, where the nucleus remains intact) offers a useful means to constrain the small- nuclear gluon density. On the other, two-photon exclusive dilepton production () allows us to study QED at field-strengths close or above the Schwinger limit (~1.5 10~V/cm). We present full simulation studies of exclusively photo-produced and high-mass dileptons in Pb-Pb collisions at the LHC
Status of Zero Degree Calorimeter for CMS Experiment
The Zero Degree Calorimeter (ZDC) is integral part of the CMS experiment,
especially, for heavy ion studies. The design of the ZDC includes two
independent calorimeter sections: an electromagnetic section and a hadronic
section. Sampling calorimeters using tungsten and quartz fibers have been
chosen for the energy measurements. An overview of the ZDC is presented along
with a current status of calorimeter's preparation for Day 1 of LHC.Comment: 8 pages, 5 figures, 1 table, to appear in the proceedings of CALOR06,
June 5-9, 2006 Chicago, US
Systematic study of high- hadron and photon production with the PHENIX experiment
The suppression of hadrons with large transverse momentum () in
central Au+Au collisions at = 200 GeV compared to a binary
scaled p+p reference is one of the major discoveries at RHIC. To understand the
nature of this suppression PHENIX has performed detailed studies of the energy
and system-size dependence of the suppression pattern, including the first RHIC
measurement near SPS energies. An additional source of information is provided
by direct photons. Since they escape the medium basically unaffected they can
provide a high baseline for hard-scattering processes.
An overview of hadron production at high in different colliding
systems and at energies from GeV will be
given. In addition, the latest direct photon measurements by the PHENIX
experiment shall be discussed.Comment: 6 pages, 3 figures, Proceeding for the Conference Strangeness in
Quark Matter, Levoca, Slovakia, June 24-29, 200
Relevance of baseline hard proton-proton spectra for high-energy nucleus-nucleus physics
We discuss three different cases of hard inclusive spectra in proton-proton
collisions: high single hadron production at 20 GeV and
at = 62.4 GeV, and direct photon production at = 200 GeV;
with regard to their relevance for the search of Quark Gluon Plasma signals in
A+A collisions at SPS and RHIC energies.Comment: Proceeds. Hot Quarks 2004 Int. Workshop on the Physics of
Ultrarelativistic Nucleus-Nucleus Collisions. 26 pages. 26 figs. [minor
corrs., refs. added
- …