THE INFLUENCE OF NET QUARKS ON YIELDS AND RAPIDITY SPECTRA OF IDENTIFIED HADRONS
Within a quark combination model, we study systematically the yields and rapidity spectra of various hadrons in central Au + Au collisions at $\sqrt{s_{\rm NN}} = 200\ {\rm GeV}$. We find that considering the difference in rapidity between net quarks and newborn quarks, the data of multiplicities, rapidity distributions for π±, K±, $p(\bar{p})$ and, in particular, the ratios of charged antihadron to hadron as a function of rapidity, can be well described. The effects of net quarks on various hadrons are analyzed, and the rapidity distributions for $K^{0}_{s}$, $\Lambda(\bar{\Lambda})$, $\Sigma^{+}(\bar{\Sigma}{}^{-})$, $\Xi^{-}(\bar{\Xi}^{+})$ and $\Omega^{-}(\bar{\Omega}^{+})$ are predicted. We discuss the rapidity distribution of net baryons, and find that it reflects exactly the energy loss of colliding nuclei.

title: Hadron Yield Correlation in Combination Models in High Energy AA Collisions
abstract: We study the hadron yield correlation in the combination models in high energy heavy ion collisions. We derive the relationship between the average yields of different hadrons produced in the combination of a system consisting of equal number of quarks and antiquarks. We present the results for the directly produced hadrons as well as those for the final hadrons including the strong and electromagnetic decay contributions. We also study the net quark influence by considering the case when the number of quarks is larger than that of the antiquarks. We make comparison with the data wherever possible.

title: Charm hadron production at RHIC in combination model
abstract: We investigate the charm hadron production in relativistic heavy-ion collisions with the quark combination model. The $p_{T}$ dependencies of the charm baryon to meson ratios such as $\frac{\Lambda_{c}+\bar{\Lambda}_{c}}{D^{0}+\bar{D}^{0}}$, $\frac{\Lambda_{c}+\bar{\Lambda}_{c}}{D^{+}+D^{-}}$ and $\frac{\Lambda_{c}+\bar{\Lambda}_{c}}{D_{s}^{+}+D_{s}^{-}}$ in Au+Au collisions at 200 GeV are obtained. The charm baryon enhancement in the intermediate $p_{T}$ range is very prominent, which further, together with the strangeness enhancement, affect the charm hadron ratios and lead to a $\sim17%$ larger charm cross-section given by PHENIX. The dependencies of the charm hadron ratios on energy, centrality, and other parameters are also investigated. Predictions of the charm hadron ratios for the upgrade of RHIC and for LHC are presented.

title: The nearest correlation in rapidity and the multiplicity distribution in e+e- annihilation
abstract: The authors discuss the combination rule of quarks controlled by the nearest correlation in rapidity. The average yields of mesons, baryons and the multiplicity spectra produced by stochastic accumulation of N pairs of quarks are given. Using the relation between the average yields of quark pairs and energy, which is in fact universal, they calculate the observed yields of meson, baryon and the multiplicity distribution in e+e- annihilation. Comparisons are made of their prediction with the experimental data and the negative binomial distribution.

title: Multiplicity distributions in hadron-hadron collisions based on the universality ansatz
abstract: Recent experiments on small-${p}_{T}$ hadron production in $\mathrm{pp}$ collisions have shed new light on the apparent violation of the universality ansatz by the fact that the multiplicity dispersion in hadron-hadron collisions is much larger than that in ${e}^{+}{e}^{\ensuremath{-}}$ collisions. We present a model based on the universality ansatz, among other things. This model reproduces qualitatively the hadron multiplicity distributions in $\mathrm{pp}$ collisions over a wide range of energies. Within our framework, this essentially resolves the discrepancy stated above. In our approach the universality ansatz is also found to be applicable to the diffractive component events. This is supported by the inclusive $x$-distribution data having various specified number of prongs in the final states.

title: A Study of elliptic flows in a quark combination model
abstract: We carry out a detail study of elliptic flows in Au-Au collisions at 200 AGeV in a quark combination model. We find that elliptic flow data for a variety of hadrons can be well reproduced except pions if constituent quarks with equal parallel transverse momenta combine into initially produced hadrons. In a combination mechanism where initial hadrons are formed by quarks with unequal parallel transverse momenta, theoretical predictions agree with data for all available hadrons including pions. The mass hierarchy at low transverse momenta in elliptic flows can be understood in the same quark combination mechanism as in the mediate range of transverse momenta.

title: Measurement of the near-threshold e+e- --> D(*)+/-D(*)-/+ cross section using initial-state radiation.
abstract: We report a measurement of the exclusive e+e- -->D(*)+/-D*-/+ cross section as a function of center-of-mass energy near the D(*)+/-D*-/+ threshold with initial-state radiation. A partial reconstruction technique is used to increase the efficiency and to suppress background. The analysis is based on a data sample collected with the Belle detector with an integrated luminosity of 547.8 fb(-1).

title: Pair-produced heavy particle topologies: MSSM neutralino properties at the LHC from gluino/squark cascade decays
abstract: Processes of the form pp → anything → XiXj → $x\bar{x}$ + $y\bar{y}$ + notE are studied via a technique that may be viewed as an adaptation of time-honoured Dalitz plot analyses. Xi and Xj are new heavy states (with i, j =1, . . .,n), which may be identical or distinct; and $x\bar{x}$ and $y\bar{y}$ are necessarily distinct standard model (SM) fermion pairs whose invariant masses can be measured. A Dalitz-like plot of said invariant masses, $M(x\bar{x})$ versus $M(y\bar{y})$, exhibits a topology connected to the masses and specific decay chains of Xi and Xj. Aside from relatively minor details, observed patterns consist of a collection of box and wedge shapes. This collection is model-dependent: comparison of the observed pattern to the possibilities for a specific model yields information on which new particle pair combinations are actually being produced, information beyond that extractable from conventional one-dimensional invariant mass distributions. The technique is illustrated via application to the minimal supersymmetric standard model (MSSM) process pp → $ \tilde{g}\tilde{g},\tilde{g}\tilde{q},\tilde{q}\tilde{q} \to \widetilde{\chi}_i^0 \widetilde{\chi}_j^0$ → e+e- + μ+μ- notE. Here the heavy states are neutralinos $\widetilde{\chi}_i^0$ (i = 2,3,4) - note that $\widetilde{\chi}_1^0$ is excluded - which are produced in gluino/squark ($\tilde{g}$/$\tilde{q}$) cascade decay chains. Even with fairly modest expectations for the LHC performance during the first few years, this method still provides substantial insight into the neutralino mass spectrum and couplings if gluino/squark masses are relatively low (≃ 400 GeV).

title: Measurement of azimuthal asymmetries in inclusive production of hadron pairs in e(+)e(-) annihilation at Belle.
abstract: The Collins effect connects transverse quark spin with a measurable azimuthal dependence in the yield of hadronic fragments around the quark's momentum vector. Using two different reconstruction methods, we find evidence of statistically significant azimuthal asymmetries for charged pion pairs in e(+)e(-) annihilation at a center-of-mass energy of 10.52 GeV, which can be attributed to a transverse polarization of the primordial quarks. The measurement was performed using a sample of 79 x 10(6) hadronic events collected with the Belle detector.

title: Observation of a chi'(c2) candidate in gamma gamma ---> D anti-D production in Belle

title: Measurement of masses and branching ratios of Xi(+)(c) and Xi(0)(c) baryons
abstract: Reference EPFL-ARTICLE-154475doi:10.1016/j.physletb.2004.11.038View record in Web of Science Record created on 2010-11-05, modified on 2017-05-12