Measurement of electron-muon correlations from semi-leptonic D decay in 200 GeV p + p collisions at RHIC-PHENIX

Charm production is a valuable probe of the early stages of a heavy ion collision. Correlated electron-muon pairs are a signature of semi-leptonic D decays, and a measurement of D mesons provides information on charm quark energy loss in the hot medium. The energy loss of heavy quarks is still not fully understood, so it is vital to investigate different decay channels of charm mesons to better understand this process. Measurements of electron-muon pairs suffer less from background than e ⁺ e ⁻ or μ⁺μ⁻ pairs since neither direct lepton production nor resonance decays produce this type of correlated signal. Another advantage is that because electrons are measured in the central arms and muons are measured in the forward region in PHENIX, open charm can be probed in a rapidity region different from previous dilepton measurements. Studying electron-muon pairs in p + p collisions provides an important baseline for the study of these processes in d + Au and Au + Au collisions. The data in this analysis was obtained during the 2006 RHIC run of p + p collisions at 200 GeV. The current status of this analysis will be presented.     

Jet studies for 5.5TeV Pb+Pb collisions via di-hadron correlations

Understanding the energy loss mechanisms in hot and dense QCD matter is an important aspect of phase diagram exploration at the Relativistic Heavy Ion Collider (RHIC). A wide variety of experimental studies are devoted to this subject. With the start of the experimental program at the Large Hadron Collider (LHC) such studies will be taken to a new energy domain lending to crucial new insights on the properties of the new state of matter. We investigate the possibility of utilizing di-hadron correlation techniques for probing the medium created in heavy ion collisions at the 5.5 TeV with a generic hadron detector. We discuss characterization of the jet yields, fragmentation functions, and energy estimates on near- and away- sides in triggered di-hadron correlations.     

Study of neutral-charged particle correlations in high energy collisions

Recent experiments at Serpukhov, NAL, and CERN indicate a strong correlation between neutral and charged pions produced in high energy collisions, in contrast to the trend shown by data at lower energies. This study of the energy and charge dependence of these correlations indicates that they do not depend upon the initial state particles and that they are in reasonable agreement with the critical fluid gas model. These high energy correlation data are also studied in terms of a semi-inclusive Koba-Nielsen-Olesen scaling relation.     

Light particle correlations in intermediate energy heavy ion collisions

Various light particle coincidence techniques will be reviewed that were employed to study the emission of energetic light particles in nucleus-nucleus collisions at energies above 10 MeV/nucleon. Several reaction mechanisms have been shown to contribute to the emission of energetic light particles, ranging from the sequential statistical decay of excited projectile residues, direct breakup and knock-out reactions, to multistep emission processes that can be rather well described in terms of the concept of local thermal equilibrium.     

Transverse radial expansion in nuclear collisions and two particle correlations

At the very first stage of an ultra-relativistic nucleus–nucleus collision new particles are produced in individual nucleon–nucleon collisions. In the transverse plane, all particles from a single NN collision are initially located at the same position. The subsequent thermalization and transverse radial expansion of the system create strong position-momentum correlations and lead to characteristic rapidity, transverse momentum, and azimuthal correlations among the produced particles.     

Three particle inclusive correlations from relativistic heavy ion collisions

The life-time of the first excited member of the ground-state band in¹⁰¹Zr has been determined to 0.9(3) ns through the measurement of γ-γ-delayed coincidences with Ge detectors at the fission-product separator JOSEF. The result shows that this nucleus is strongly deformed with |ß|=0.32(6). This finding provides further important evidence for the fact that the odd-mass nuclei at A ~ 100 with more than 59 neutrons are good rotors.     

Measurements of high pT light fragments at CM 90° in 800 A MEV C + C collisions

The spectra of high-p_T fragments have been measured at CM 90° in 800 A MeV C + C collisions for p_T up to 1.8 GeV/c (proton), 2.5 GeV/c (deuteron) and 2.8 GeV/c (triton) at the Bevalac. Invariant cross sections were measured down to eight orders of magnitude lower than those for production of low momentum protons. The proton spectrum shows a significant deviation from the Boltzmann shape in the high-energy region. The spectra of deuterons and tritons are explained well by, respectively, squaring and cubing the observed proton spectra.     

Space-momentum correlations in 8 AGeV Au+Au collisions

Within the RQMD model, space-momentum correlations, i.e. the correlations between final momentum anisotropy and initial eccentricity, are studied for 8 AGeV Au+Au events classified according to the multi-particle azimuthal correlations. The results show that the final elliptic flow fluctuations depend on the initial collision geometry. There are clear space-momentum correlations for nucleons during the whole dynamical evolution of the collisions.     

Space-momentum correlations in 8 AGeV Au+Au collisions

Within the RQMD model, space-momentum correlations, i.e. the correlations between final momentum anisotropy and initial eccentricity, are studied for 8 AGeV Au＋Au events classified according to the multi-particle azimuthal correlations. The results show that the final elliptic flow fluctuations depend on the initial collision geometry. There are clear space-momentum correlations for nucleons during the whole dynamical evolution of the collisions.     

Observation of K+d correlations from pA collisions

Results of a first experiment on (K^+p) and (K^+d) correlations from proton-carbon (pC) and proton-deuteron (pd) interactions at beam energies above and much below the threshold for elementary kaon production in nucleon-nucleon reactions ( T _NN = 1580 MeV) are discussed. These data, obtained with the ANKE spectrometer at COSY-Jülich, provide first direct evidence for K⁺ production via the two-step mechanism and an indication for a cluster mechanism. It is shown that both processes contribute significantly in pC collisions at 1200 MeV, while they are strongly suppressed at 2300 MeV and also in pd-interactions at 1344 MeV. It is emphasized that the underlying kinematics can be exploited to distinguish between these reaction mechanisms. Received: 26 November 2002 / Accepted: 26 March 2003 / Published online: 20 May 2003     

Charged particle correlations at y = 0 in pp collisions at the CERN ISR

Measurements of the double differential cross sections for ππ and pπ production in pp collisions at the CERN ISR are presented for 5 c.m. energies $\text{s}\text{= 22, 30, 44, 53, 62}\text{GeV}$. Charge and transverse momentum correlations are also reported.     

Two-kaon correlations in central Pb+Pb collisions at 158 a GeV/c

Two-particle interferometry of positive kaons is studied in Pb+Pb collisions at mean transverse momenta approximately 0.25 and 0.91 GeV/c. A three-dimensional analysis was applied to the lower p(T) data, while a two-dimensional analysis was used for the higher p(T) data. We find that the source-size parameters are consistent with the m(T) scaling curve observed in pion-correlation measurements in the same collisions, and that the duration time of kaon emission is consistent with zero within the experimental sensitivity.     

Neutral-charged particle correlations in proton-proton collisions in the framework of a two-component model

The data on \(\bar N_0 \left( {n\_} \right)\) , the average number of neutrals as a function ofn _?, the number of negatively charged particles produced, is fitted at 69, 205 and 303 GeV/c. The two-component model used for the charged multiplicity distributionP _n, is one which envisages two distinct types of collisions and is the simplest such model consistent with charge conservation. We find that the data on \(\bar N_0 \left( {n\_} \right)\) can be fitted reasonably well. Further, our results, based on this model forP _n, suggest that at 50 GeV/c, \(\bar N_0 \left( {n\_} \right)\) should increase linearly withn _?and that neutral-negative correlations should be present in the central component.     

Reconstruction of hadronization stage in Pb+Pb collisions at 158 A GeV/c

Recent data on hadron multiplicities in central Pb+Pb collisions at 158 A GeV/c at mid-rapidity are analyzed within the concept of chemical freeze-out. A non-uniformity of the baryon chemical potential along the beam axis is taken into account. An approximate analytical solution of the hydrodynamic equations for a chemically frozen Boltzmann-like gas is found. The Cauchy conditions for hydrodynamic evolution of the hadron resonance gas are fixed at the thermal freeze-out hypersurface from analysis of one-particle momentum spectra and HBT correlations. The proper time of chemical freeze-out and physical conditions at the hadronization stage, such as energy density and averaged transverse velocity, are found.     

Extended q -euler numbers and polynomials associated with fermionic p -adic q -integral on Z p

The purpose of this paper is to construct extended q-Euler numbers and polynomials related to fermionic p-adic q-integral on ℤ _p . By evaluating a multivariate p-adic q-integral on ℤ _p , we give new explicit formulas related to these numbers and polynomials.     

Inclusive two-particle correlations in 40 GeV/c π−p collisions and particle production mechanisms

Inclusive two-particle correlations in rapidity variables between π⁺π^?, π⁺π⁺ and π^?π^? obtained in 40 GeV π^?p collisions are discussed in the framework of the Mueller Regge model and the multiperipheral cluster model. The data show features similar to the data reported at much higher energies from the CERN ISR. This behaviour is more easily understood from the multiperipheral cluster model. Data on transverse momentum correlations in the same reactions can be qualitatively understood from the same model.