Heavy Ion Physics Program in CMS Experiment

We present the capabilities of the CMS experiment to explore the heavy-ion physics program offered by the CERN Large Hadron Collider (LHC). The prime goal of this research is to test the fundamental theory of the strong interaction (QCD) in extreme conditions of temperature, density and parton momentum fraction by colliding nuclei at energies of sqrt(s_NN) = 5.5 TeV. This presentation will give the overview of the potential of the CMS to carry out a full set of representative Pb-Pb measurements both in "soft" and "hard" regimes. Measurements include "bulk" observables -- charged hadron multiplicity, low pT inclusive hadron identified spectra and elliptic flow -- which provide information on the collective properties of the system; as well as perturbative processes - such as quarkonia, heavy-quarks, jets, gamma-jet, and high pT hadrons -- which yield "tomographic" information of the hottest and densest phases of the reaction.Comment: 8 pages, 8 figures - To appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennesse

Triggering on Hard Probes in Heavy-Ion Collisions with the CMS Experiment at the LHC

Studies of heavy-ion collisions at the LHC will benefit from an array of qualitatively new probes not readily available at lower collision energies. These include fully formed jets at ET > 50 GeV, Z0's and abundantly produced heavy flavors. For Pb+Pb running at LHC design luminosity, the collision rate in the CMS interaction region will exceed the available bandwidth to store data by several orders of magnitude. Therefore an efficient trigger strategy is needed to select the few percent of the incoming events containing the most interesting signatures. In this report, we will present the heavy-ion trigger strategy developed for the unique two-layer trigger system of the CMS experiment which consists of a ``Level-1'' trigger based on custom electronics and a High Level Trigger (HLT) implemented using a large cluster of commodity computers.Comment: 4 pages, 1 figure, To appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennesse

Measurements of high-pT probes in heavy ion collisions at CMS

The capabilities of the CMS detector at the LHC will be described for measuring high-pT hadrons, photons and jets in heavy ion collisions. Detailed simulations of various studies planned with the CMS apparatus, including charged particle tracking, jet reconstruction using calorimetry, dimuon and isolated photon detection and the measurement of in-medium fragmentation functions using high-pT photon-jet correlations will be discussed.Comment: 4 pages, 5 figures - To appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennessee, US

Heavy Ion Physics with CMS detector

We will present the capabilities of the CMS experiment to explore the heavy-ion physics programme offered by the CERN Large Hadron Collider (LHC). Collisions of lead nuclei at energies $\sqrt{s_{_{NN}}}$ = 5.5 TeV, will probe quark and gluon matter at unprecedented values of energy density. The prime goal of this research is to study the fundamental theory of the strong interaction (QCD) in extreme conditions of temperature, density and parton momentum fraction. This presentation will give the overview of the potential of the CMS to carry out a full set of representative Pb-Pb measurements both in ''soft'' and ''hard'' regimes. Measurements include ``bulk'' observables -- charged hadron multiplicity, low $p_{\rm T}$ inclusive hadron identified spectra and elliptic flow -- which provide information on the collective properties of the system; as well as perturbative processes -- such as quarkonia, heavy-quarks, jets, $\gamma$-jet, and high $p_{\rm T}$ hadrons --- which yield ``tomographic'' information of the hottest and densest phases of the reaction

Background subtraction and jet quenching on jet reconstruction

In order to assess the ability of jet observables to constrain the characteristics of the medium produced in heavy-ion collisions at the LHC, we investigate the influence of background subtraction and jet quenching on jet reconstruction, with focus on the dijet asymmetry as currently studied by ATLAS and CMS. Using a toy model, we examine the influence of different background subtraction methods on dijet momentum imbalance and azimuthal distributions. We compare the usual jet-area based background subtraction technique and a variant of the noise-pedestal subtraction method used by CMS. The purpose of this work is to understand what are the differences between the two techniques, given the same event configuration. We analyze the influence of the quenching effect using the Q-PYTHIA Monte Carlo on the previous observables and to what extent Q-PYTHIA is able to reproduce the CMS data for the average missing transverse momentum that seems to indicate the presence of large angle emission of soft particles.Comment: 4 pages, 3 figures, Proceedings for Hard Probes 201

Quarkonia measurements in heavy-ion collisions in CMS

The production of quarkonia is one of the most promising signals at the LHC for the study of the production properties of Quark Gluon Plasma. In addition to the J/psi, the extent to which upsilon is suppressed should give much insight into the new state of matter. The large muon acceptance and the high precision tracker make the CMS detector ideal for studies of this physics. In this note, the performance of the CMS detector for quarkonia measurements in heavy-ion collisions in the dimuon channel is presented. Dimuon reconstruction efficiencies and mass resolution are calculated using detailed detector simulation. Mass spectra and signal to background ratios are estimated with a fast Monte Carlo program. Results obtained with the fast Monte Carlo are compared with more detailed simulations

Opinion: Chemical--Mesoscopics..for the Mesoparticles Reactivity Explanation

The estimation of chemical particles reactivity and the determination of chemical reactions direction are the actual theme in new scientific trend - Chemical Mesoscopics. Paper includes the proposal about the using the theory of free energy linear dependence from physical organic chemistry and their applications for prognosis of reactions flowing. The semi-empiric constants is given according to mesoscopic physics definitions as well as the transformed Kolmogorov-Avrami equation is discussed. It is the development of Chemical Mesoscopics for organic reactivity estimation including nanostructures reactivit

Algorithm for jet identification and reconstruction in densly populated calorimetric system

The jet reconstruction algorithm is developed under the condition of high particle density in the calorimetric system. The performance of reconstruction of hard QCD jets with initial parton energies 50-300 GeV is studied in central Pb--Pb collisions with a modified cone jet finder which includes an algorithm for event-by-event background subtraction. The heavy ion background is simulated using the HIJING Monte-Carlo generator with dNch/dy = 5000. Results on the achieved jet reconstruction efficiency, purity, energy and spatial resolution are presented