<Emphasis Type="Italic">J</Emphasis>/<Emphasis Type="Italic">ψ</Emphasis> suppression and <Emphasis Type="Italic">p</Emphasis><Subscript><Emphasis Type="Italic">T</Emphasis></Subscript> spectra in RHIC and LHC energy collisions

In a hydrodynamic model, we have studied J/ψ production in Au+Au/Cu+Cu collisions at RHIC energy, GeV. At the initial time, J/ψ’s are randomly distributed in the fluid. As the fluid evolves in time, the free streaming J/ψ’s are dissolved if the local fluid temperature exceeds a threshold temperature T _J/ψ . Sequential melting of charmonium states (χ _c , ψ ^′ and J/ψ), with melting temperatures , T _J/ψ ≈2T _c and feed-down fraction F≈0.3, explains the PHENIX data on the centrality dependence of J/ψ suppression in Au+Au collisions. J/ψ p _T spectra and the nuclear modification factor in Au+Au collisions are also well explained in the model. The model however overpredicts the centrality dependence of J/ψ suppression in Cu+Cu collisions by 20–30%. The J/ψ p _T spectra are underpredicted by 20–30%. The model predicts that in central Pb+Pb collisions at LHC energy,  GeV, J/ψ’s are suppressed by a factor of ∼10. The model predicted a J/ψ p _T distribution in Pb+Pb collisions at LHC is similar to that in Au+Au collisions at RHIC.     

Study of B c → J / ψ π , η c π decays with?perturbative?QCD?approach

The B _c →J/ψ π, η _c π decays are studied with the perturbative QCD approach. It is found that the form factors and for the B _c →J/ψ, η _c transitions and the branching ratios are sensitive to the parameters ω, v, f _J/ψ and , where ω and v are the parameters of the charmonium wave functions for a Coulomb potential and the harmonic-oscillator potential, respectively, and f _J/ψ and are the decay constants of the J/ψ and η _c mesons, respectively. The large branching ratios and the clear signals of the final states make the B _c →J/ψ π, η _c π decays the prospective channels for measurements at the hadron colliders.     

Negative elliptic flow of J/ψ’s: A qualitative signature for charm collectivity at RHIC

We discuss one of the most prominent features of the very recent preliminary elliptic flow data of J/ψ-mesons from the PHENIX Collaboration (PHENIX Collaboration (C. Silvestre), arXiv:0806.0475 [nucl-ex]). Even within the rather large error bars of the measured data a negative elliptic flow parameter (v₂) for J/ψ in the range of p _T = 0.5-2.5 GeV/c is visible. We argue that this negative elliptic flow at intermediate p_T is a clear and qualitative signature for the collectivity of charm quarks produced in nucleus-nucleus reactions at RHIC. Within a parton recombination approach we show that a negative elliptic flow puts a lower limit on the collective transverse velocity of heavy quarks. The numerical value of the transverse flow velocity for charm quarks that is necessary to reproduce the data is (charm) ∼ 0.55-0.6c and therefore compatible with the flow of light quarks.     

Quarkonia measurements with STAR

We report results on quarkonium production from the STAR experiment at the Relativistic Heavy-Ion Collider (RHIC). J/ψ spectra in p+p and Cu+Cu collisions at  GeV with transverse momenta in the range of 0.5–14 GeV/c and 5–8 GeV/c, respectively, are presented. We find that for p _T >5 GeV/c yields in p+p collisions are consistent with those in minimum-bias Cu+Cu collisions scaled with the respective number of binary nucleon-nucleon collisions. In this range the nuclear modification factor, R _AA , is measured to be 0.9±0.2 (stat). For the first time at RHIC, high-p _T J/ψ-hadron correlations were studied in p+p collisions. Implications from our measurements on J/ψ production mechanisms, constraints on open bottom yields, and J/ψ dissociation mechanisms at high-p _T are discussed. In addition, we give a brief status of measurements of ϒ production in p+p and Au+Au collisions and present projections of future quarkonia measurements based on an upgrades to the STAR detector and increased luminosity achieved through stochastic cooling of RHIC.     

Transverse-momentum dependence of <Emphasis Type="Italic">J</Emphasis>/<Emphasis Type="Italic">ψ</Emphasis> shadowing effects

We present a new approach to estimate the effect of gluon shadowing in nucleus + nucleus collisions and its consequences on the J/ψ production yield. Using kinematical information available from the measured J/ψ production in proton + proton collisions at  GeV, we build a Glauber Monte Carlo code which takes into account shadowing in two alternative ways: multiple-scattering corrections or Q ² evolution of parton densities. We exploit the dependence of these different parameterizations to the J/ψ transverse momentum and we give the first predictions on the resulting p _T dependence of the nuclear modification factor in deuteron + gold collisions at the same energy.     

Charmonium dissociation and recombination at RHIC and LHC

Charmonium production at heavy-ion colliders is considered within the comovers-interaction model. The formalism is extended by including possible secondary J/ψ production through recombination and an estimate of recombination effects is made without adjusting the model parameters. The comovers-interaction model also includes a comprehensive treatment of initial-state nuclear effects, which are discussed in the context of such high energies. With these tools, the model properly describes the centrality and the rapidity dependence of experimental data at RHIC energy,  GeV, for both Au+Au and Cu+Cu collisions. Predictions for LHC,  TeV, are presented and the assumptions and extrapolations involved are discussed.     

Centrality dependence of v 2 in Au + Au at \sqrt{s_{NN}}=200 GeV

One of the most striking results is the large elliptic flow (v ₂) at RHIC. Detailed mass and transverse momentum dependence of elliptic flow are well described by ideal hydrodynamic calculations for p _T<1 GeV/c, and by parton coalescence/recombination picture for p _T=2–6 GeV/c. The systematic error on v ₂ is dominated by so-called “non-flow effects”, which are correlations other than flow, such as resonance decays and jets. It is crucial to understand and reduce the systematic error from non-flow effects in order to understand the underlying collision dynamics. In this paper, we present the centrality dependence of v ₂ with respect to the first harmonic event plane at ZDC-SMD (v ₂{ZDC-SMD}) in Au + Au collisions at  GeV. A large rapidity gap (|Δη|>6) between midrapidity and the ZDC-SMD could enable us to minimize possible non-flow contributions. We compare the results of v ₂{ZDC-SMD} with v ₂{BBC}, which is measured by event plane determined at |η|=3.1–3.9. Possible non-flow contributions in those results will be discussed.     

J/ψ suppression vs centrality at forward and mid-rapidity in Au+Au collisions at RHIC in colour screening mechanism

We extend our previous formalism [Phys. Lett. B 656 45 (2007)] on J/ψ suppression at midrapidity using the colour screening framework. Our formalism is more general as the complete rapidity, transverse momentum and centrality dependence including J/ψ suppression at forward as well as mid-rapidity can be computed directly from it. We have assumed that QGP fluid is expanding obeying Bjorken’s boost invariant scaling law and bag model EOS is used. Sequential melting of χ _c (1P) as well as ψ′ (2S) higher resonances is incorporated. We find that our model shows a reasonable agreement with the mid and forward rapidity data. Furthermore, we observe a larger suppression at forward rapidity in our model which is again well supported by the PHENIX data.     

<Emphasis Type="Italic">X</Emphasis>(3872) and other possible heavy molecular states

We perform a systematic study of the possible molecular states composed of a pair of heavy mesons such as , , in the framework of the meson exchange model. The exchanged mesons include the pseudoscalar, scalar and vector mesons. Through our investigation, we find the following results. (1) The structure X(3764) is not a molecular state. (2) There exists strong attraction in the range r<1 fm for the system with J=0,1. If future experiments confirm Z ⁺(4051) as a loosely bound molecular state, its quantum number is probably J ^P =0⁺. Its partner state Φ ^**0 may be searched for in the π ⁰ χ _c1 channel. (3) Vector meson exchange provides strong attraction in the channel together with pion exchange. A bound state solution may exist with a reasonable cutoff parameter Λ∼1.4 GeV. X(3872) may be accommodated as a molecular state dynamically although drawing a very definite conclusion needs further investigation. (4) The molecular state may exist.     

Angular distributions of leptons from J/ψ’s produced in 920?GeV fixed-target proton-nucleus collisions

A study of the angular distributions of leptons from decays of J/ψ’s produced in p-C and p-W collisions at has been performed in the J/ψ Feynman-x region −0.34<x _F <0.14 and for J/ψ transverse momenta up to 5.4 GeV/c. The data were collected by the HERA-B experiment at the HERA proton ring of the DESY laboratory. The results, based on a clean selection of 2.3×10⁵ J/ψ’s reconstructed in both the e ⁺ e ⁻ and μ ⁺ μ ⁻ decay channels, indicate that J/ψ’s are produced polarized. The magnitude of the effect is maximal at low p _T . For p _T >1 GeV/c a significant dependence on the reference frame is found: the polar anisotropy is more pronounced in the Collins-Soper frame and almost vanishes in the helicity frame, where, instead, a significant azimuthal anisotropy arises. Many thanks to Antonio Vitale (1943–2008). Deceased. Supported by the Foundation for Fundamental Research on Matter (FOM), 3502 GA Utrecht, The Netherlands. Visitor from Dipartimento di Energetica dell’ Università di Firenze and INFN Sezione di Bologna, Italy. Visitor from P.N. Lebedev Physical Institute, 117924 Moscow B-333, Russia. Visitor from Moscow Physical Engineering Institute, 115409 Moscow, Russia. Visitor from Moscow State University, 119992 Moscow, Russia. Visitor from Institute for High Energy Physics, Protvino, Russia. Visitor from High Energy Physics Institute, 380086 Tbilisi, Georgia. Also from Fondazione Giuseppe Occhialini, 61034 Fossombrone (Pesaro Urbino), Italy. Supported by the CICYT contract AEN99-0483. Supported by the German Research Foundation, Graduate College GRK 271/3.     

Identified hadron production at high transverse momenta in p+ p collisions at $\sqrt{s_{NN}}=200$ GeV in STAR

We report the transverse momentum (p _T ) distributions for identified charged pions, protons and anti-protons using events triggered by high deposit energy in the Barrel Electro-Magnetic Calorimeter (BEMC) from p+p collisions at  GeV. The spectra are measured around mid-rapidity (|y|<0.5) over the range of 3<p _T <15 GeV/c with particle identification (PID) by the relativistic ionization energy loss (rdE/dx) in the Time Projection Chamber (TPC) of the Solenoidal Tracker at RHIC (STAR). The charged pion, proton and anti-proton spectra at high p _T are compared with published results from minimum bias triggered events and the Next-Leading-Order perturbative quantum chromodynamic (NLO pQCD) calculations (DSS, KKP and AKK 2008). In addition, we present the particle ratios of π ⁻/π ⁺, , p/π ⁺ and in p+p collisions.     

Separated cross-sections in \pi^{0}_{} electroproduction at threshold at Q2 = 0.05GeV2/c2

The differential cross-sections σ₀ = σ_T + εσ_L , σ_LT , and σ_TT of electroproduction from the proton were measured from threshold up to an additional center-of-mass energy of 40MeV, at a value of the photon four-momentum transfer of Q ² = 0.05 GeV²/c² and a center-of-mass angle of θ = 90^° . By an additional out-of-plane measurement with polarized electrons σ_LT' was determined. This showed for the first time the presence of an imaginary part of the s -wave above the threshold, which is usually interpreted as a unitary cusp. The predictions of the Heavy Baryon Chiral Perturbation Theory (HBChPT) are in disagreement with these data. On the other hand, the data are somewhat better predicted by the MAID phenomenological model and are in good agreement with the dynamical model DMT.     

Analysis of Ωb? (bss) and Ωc0 (css) with QCD sum rules

We calculate the masses and the pole residues of the heavy baryons Ω _c ⁰(css) and Ω _b ⁻(bss) with the QCD sum rules. The numerical values  GeV (or  GeV) and  GeV (or  GeV) are in good agreement with the experimental data.     

MD simulation of concentrated polymer solutions: Structural relaxation near the glass transition

We examine by molecular dynamics simulations the relaxation of polymer-solvent mixtures close to the glass transition. The simulations employ a coarse-grained model in which polymers are represented by bead-spring chains and solvent particles by monomers. The interaction parameters between polymer and solvent are adjusted such that mixing is favored. We find that the mixtures have one glass transition temperature T _g or critical temperature T _c of mode-coupling theory (MCT). Both T _g and T _c (> T _g decrease with increasing solvent concentration . The decrease is linear for the concentrations studied (up to = 25%. Above T _c we explore the structure and relaxation of the polymer-solvent mixtures on cooling. We find that, if the polymer solution is compared to the pure polymer melt at the same T, local spatial correlations on the length scale of the first peak of the static structure factor S(q) are reduced. This difference between melt and solution is largely removed when comparing the S(q) of both systems at similar distance to the respective T _c. Near T _c we investigate dynamic correlation functions, such as the incoherent intermediate scattering function (t), mean-square displacements of the monomers and solvent particles, two non-Gaussian parameters, and the probability distribution P(ln r;t) of the logarithm of single-particle displacements. In accordance with MCT we find, for instance, that (t) obeys the time-temperature superposition principle and has relaxation times which are compatible with a power law increase close (but not too close) to T _c. In divergence to MCT, however, the increase of depends on the wavelength q, small q values having weaker increase than large ones. This decoupling of local and large-length scale relaxation could be related to the emergence of dynamic heterogeneity at low T. In the time window of the relaxation an analysis of P(ln r;t) reveals a double-peak structure close to T _c. The first peak correponds to “slow” particles (monomer or solvent) which have not moved much farther than 10% of their diameter in time t, whereas the second occurs at distances of the order of the particle diameter. These “fast” particles have succeeded in leaving their nearest-neighbor cage in time t. The simulation thus demonstrates that large fluctuations in particle mobility accompany the final structural relaxation of the cold polymer solution in the vicinity of the extrapolated T _c.     

Semiclassical analysis of edge state energies in the integer quantum Hall effect

Analysis of edge-state energies in the integer quantum Hall effect is carried out within the semiclassical approximation. When the system is wide so that each edge can be considered separately, this problem is equivalent to that of a one dimensional harmonic oscillator centered at x = x_c and an infinite wall at x = 0, and appears in numerous physical contexts. The eigenvalues E_n(x_c) for a given quantum number n are solutions of the equation S(E,x_c)=π[n+ γ(E,x_c)] where S is the WKB action and 0 < γ < 1 encodes all the information on the connection procedure at the turning points. A careful implication of the WKB connection formulae results in an excellent approximation to the exact energy eigenvalues. The dependence of γ[E_n(x_c),x_c] ≡γ_n(x_c) on x_c is analyzed between its two extreme values as x_c ↦-∞ far inside the sample and as x_c ↦∞ far outside the sample. The edge-state energiesE_n(x_c) obey an almost exact scaling law of the form and the scaling function f(y) is explicitly elucidated.     

What do we really know about cold nuclear matter effects?

The measurement of charmonium suppression in relativistic heavy ion collisions is posited to be an unambiguous probe of the properties of the strongly interacting quark gluon plasma (sQGP). In hot and dense QCD matter Debye color screening prevents charm and anti-charm quark pairs from forming J/ψ mesons if the screening radius is smaller than the binding radius. However, one must have a clear understanding of the expected suppression in normal density QCD matter before interpreting any additional anomalous suppression. The PHENIX experiment has measured J/ψ production from colliding proton + proton and deuteron + gold beams at 200 GeV from the relativistic heavy ion collider (RHIC). The deuteron + gold data can be compared to the proton + proton baseline in order to establish the typical suppression in cold nuclear matter (CNM). For PHENIX, a suppression of J/ψ in cold nuclear matter is observed as one goes forward in rapidity (in the deuteron-going direction), corresponding to a region more sensitive to initial state low-x gluons in the gold nucleus. These results can be convoluted with the nuclear-environment-modified parton distribution functions, extracted from deep inelastic scattering (DIS) and Drell-Yan (DY) data, in order to estimate the J/ψ break up cross section in cold nuclear matter. One can also use a data driven method that does not rely on the assumption of the production mechanism, or PDF parameterization, to extrapolate to the heavy ion collision case. At this time both the predictions for CNM effect suppression in heavy ion collisions are somewhat ambiguous. Future results using the data acquired by the PHENIX experiment in run-6 (p + p) and run-8 (d + Au) will be vital for our understanding. These data, which are in the process of being analyzed, will provide a needed improvement in the statistical and systematic precision of constraints for CNM effects. These constraints must be improved in order to make firm conclusions concerning additional hot nuclear matter charmonium suppression in the sQGP.     

Precise predictions for Higgs production in association with a W-boson pair at ILC

Higgs-boson production in association with a W-boson pair at e ⁺ e ⁻ linear colliders is one of the important processes in probing the coupling between the Higgs boson and vector gauge bosons and discovering the signature of new physics. We describe the impact of the complete electroweak (EW) radiative corrections of to this process in the standard model (SM) at the International Linear Collider (ILC), and investigate the dependence of the lowest-order (LO) and EW next-to-leading order (NLO) corrected cross sections on the colliding energy and the Higgs-boson mass. The LO and NLO EW corrected distributions of the invariant mass of the W-boson pair and the transverse momenta of the final W-boson and Higgs boson are presented. Our numerical results show that the relative EW radiative correction (δ _ew) varies from −19.4% to 0.2% when m _H=120 GeV and grows from 300 GeV to 1.2 TeV.     

The study of light scalar mesons at BESII

The production of σ and κ in J/ψ decays is presented using 58 million J/ψ events collected at BES II detector. We also report the study of the light scalar mesons f ₀(980), f ₀(1370), f ₀(1500) and f ₀(1710) etc. in J/ψ decays.