Long-range and short-range dihadron angular correlations in central PbPb collisions at √sNN=2.76 TeV

This is the pre-print version of the Published Article, which can be accessed from the link below.First measurements of dihadron correlations for charged particles are presented for central PbPb collisions at a nucleon-nucleon center-of-mass energy of 2.76TeV over a broad range in relative pseudorapidity ( ) and the full range of relative azimuthal angle ( ). The data were collected with the CMS detector, at the LHC. A broadening of the away-side ( ) azimuthal correlation is observed at all , as compared to the measurements in pp collisions. Furthermore, long-range dihadron correlations in are observed for particles with similar values. This phenomenon, also known as the \ridge", persists up to at least j j = 4. For particles with transverse momenta (pT) of 2-4 GeV/c, the ridge is found to be most prominent when these particles are correlated with particles of pT = 2-6 GeV/c, and to be much reduced when paired with particles of pT = 10-12 GeV/c

Suppression and azimuthal anisotropy of prompt and nonprompt J/psi production in PbPb collisions at root S-NN=2.76 TeV

The nuclear modification factor RAA and the azimuthal anisotropy coefficient v2 of prompt and nonprompt (i.e. those from decays of b hadrons) J/ψ mesons, measured from PbPb and pp collisions at sNN−−−√=2.76 TeV at the LHC, are reported. The results are presented in several event centrality intervals and several kinematic regions, for transverse momenta pT>6.5 GeV/c and rapidity |y|<2.4 , extending down to pT=3 GeV/c in the 1.6<|y|<2.4 range. The v2 of prompt J/ψ is found to be nonzero, but with no strong dependence on centrality, rapidity, or pT over the full kinematic range studied. The measured v2 of nonprompt J/ψ is consistent with zero. The RAA of prompt J/ψ exhibits a suppression that increases from peripheral to central collisions but does not vary strongly as a function of either y or pT in the fiducial range. The nonprompt J/ψ RAA shows a suppression which becomes stronger as rapidity or pT increases. The v2 and RAA of open and hidden charm, and of open charm and beauty, are compared

Compound effect of EHD and surface roughness in pool boiling and CHF with R-123

This article is a post-print version of the fianl published article which may be accessed at the link below.Saturated pool boiling of R-123 at 1 bar, including the critical heat flux (CHF), was enhanced by modifying the surface characteristics and applying a high intensity electrostatic field, the latter termed electrohydrodynamic (and abbreviated EHD) enhancement. The heat flux was varied from very low values in the natural convection regime up to CHF. Experiments were performed with increasing and decreasing heat flux to study boiling hysteresis without and with EHD. Boiling occurred on the sand blasted surface of a cylindrical copper block with embedded electrical heating elements, with standardized surface parameter Pa = 3.5 μm. The electric field was generated by a potential of 5 kV to 25 kV, applied through a 40 mm diameter circular electrode of ss-304 wire mesh, aperture size 5.1 mm, located at distances of 5 - 60 mm from the surface, with most of the data obtained for 20 mm. The data for the rough surface were compared with earlier data for a smooth surface and indicated a significant increase in the heat transfer rates. EHD produced a further increase in the heat transfer rates, particularly at low heat flux values and near the CHF. Boiling hysteresis was reduced progressively by EHD and eliminated at high field strength.This work was supported by Government of Pakistan under a scholarship programme

The Case On Assessment Of Spilled Oil With Mixed Free Product In Seoul

The purpose of this study is to assess sources of contamination by analyzing the free product and oil compounds in groundwater near the Subway Station, located adjacent to the Yongsan Garrison in Seoul, Republic of Korea. All of the samples collected twice were groundwater and free product in a monitoring well. Analysis items are TPH fingerprinting, pristine/phytane ratio, alkylbenzene pattern, PAH&alkyl PAH, antioxidant, icing inhibitor, PIANO, element(C, N, H), and sulfur. Using ratio of pristine/phytane, we were able to distinguished fuel type between kerosene and JP-8 samples, which was impossible by GC/FID pattern. Alkyl benzene pattern was very effective in distinguishing between JP-8 and kerosene. It is very important that 2,4-dimethyl-6-tert-butyl phenol, an antioxidant used only for JP-8, was detected in free product samples. The concentration of sulfur in kerosene fuel is much lower than that of JP-8, and the total contents of sulfur in environmental samples can be used to differentiate the fuel type of spilled oil between kerosene and JP-8. In conclusion, according to the result of a variety of analytical methods to find the source of spilled fuel, it had been found that the fuel type detected in the tunnel of subway station and monitoring wells outside of Yongsan Garrison and the monitoring wells inside of Yongsan Garrison are the same

Forward-backward asymmetry of Drell-Yan lepton pairs in pp collisions at root s=7 TeV

A measurement of the forward-backward asymmetry (AFB) of Drell-Yan lepton pairs in pp collisions at s=7TeV is presented. The data sample, collected with the CMS detector, corresponds to an integrated luminosity of 5fb-1. The asymmetry is measured as a function of dilepton mass and rapidity in the dielectron and dimuon channels. Combined results from the two channels are presented, and are compared with the standard model predictions. The AFB measurement in the dimuon channel and the combination of the two channels are the first such results obtained at a hadron collider. The measured asymmetries are consistent with the standard model predictions. © 2012 CERN

Search for anomalous production of highly boosted ZZ bosons decaying to μ+μ−\mu^+ \mu^- in proton-proton collisions at s=7\sqrt{s}=7 TeV

Results are reported from a search for the anomalous production of highly boosted Z bosons with large transverse momentum and decaying to dimuons. Such Z bosons may be produced in the decays of new heavy particles. The search uses pp collision data at sqrt(s) = 7 TeV, corresponding to an integrated luminosity of 5.0 inverse femtobarns recorded with the CMS detector. The shape of the observed transverse-momentum distribution of Z bosons is consistent with standard model expectations. Constraints are obtained on models predicting the production of excited quarks decaying via electroweak processes. Assuming a compositeness scale that is equal to the excited quark mass as well as transition coupling strengths between Z bosons and excited quarks that are equal to standard model couplings to quarks, masses of excited quarks below 1.94 TeV are excluded at the 95% confidence level. For excited quark production via a novel contact interactions, masses below 2.22 TeV are excluded, even if the excited quarks do not couple to gluons.Peer Reviewe

Measurement of the charge asymmetry in top-quark pair production in proton–proton collisions at √s = 7 TeV

The difference in angular distributions between top quarks and antiquarks, commonly referred to as the charge asymmetry, is measured in pp collisions at the LHC with the CMS experiment. The. data sample corresponds to an integrated luminosity of 1.09 fb(-1) at a centre-of-mass energy of 7 TeV. Top-quark pairs are selected in the final state with an electron or muon and four or more jets. At least one jet is identified as originating from b-quark hadronization. The charge asymmetry is measured in two variables, one based on the pseudorapidities (eta) of the top quarks and the other on their rapidities (y). The results A(C)(eta) = -0.017 +/- 0.032 (stat.)(-0.036)(+0.025) (syst.) and A(C)(y) = -0.013 +/- 0.028 (stat.)(-0.031)(+0.029) (syst.) are consistent within uncertainties with the standard-model predictions. (C) 2012 CERN. Published by Elsevier B.V. Open access under CC BY-NC-ND license

Measurement of the charge asymmetry in top-quark pair production in proton-proton collisions at root s=7 TeV

The difference in angular distributions between top quarks and antiquarks, commonly referred to as the charge asymmetry, is measured in pp collisions at the LHC with the CMS experiment. The data sample corresponds to an integrated luminosity of 1.09fb -1 at a centre-of-mass energy of 7 TeV. Top-quark pairs are selected in the final state with an electron or muon and four or more jets. At least one jet is identified as originating from b-quark hadronization. The charge asymmetry is measured in two variables, one based on the pseudorapidities (η) of the top quarks and the other on their rapidities (y). The results ACη=-0.017±0.032(stat.)-0.036+0.025(syst.) and ACy=-0.013±0.028(stat.)-0.031+0.029(syst.) are consistent within uncertainties with the standard-model predictions. © 2012 CERN