Search for the origin of double-peak structure at RHIC by AMPT model with triggered di-jet

With a multi-phase transport （AMPT） model,a γ-jet with known production point and momentum is triggered to search for the origin of double-peak structure in di-hadron azimuthal correlation in central Au＋Au collisions at RHIC energy.The different configurations of triggered γ-jet produce different shapes of medium responses.The key of the double-peak structure is found to be a strong shadowing effect of dense core,which is related to transverse expansion and radial flow of partonic matter.     

Strange quark dynamics on hot dense matter under the extreme condition

Production and properties of φ-meson under the extreme hot dense matter which is formed in Au ＋ Au collisions at RHIC energy have been briefly reviewed.The issues are focused on transverse momentum （p T ） spectra of φ,elliptic flow of φ,nuclear modification factor of φ,the ratio of Ω（p T ）/φ（p T ） versus p T,the ratio of Ω（p T /3）/φ（p T /2） versus p T /n q,spin alignment of φ and the enhancement of φ etc.These observables give the significant information of the strange quark dynamics in hot dense matter under the extreme condition.     

Effect of parton cascade to medium

Jet quenching has been proposed as a probe of the properties of the strongly interacting quarkgluon-plasma in high energy heavy ion collisions.At the meantime,it is also important to study the excitation of medium by propagating jets.Based on Boltzmann equation,a Monte Carlo was constructed to simulate the elastic collisions with thermal partons by energetic jets.Medium modification due to jet-medium interaction has been studied within this model in a uniform medium.     

Parton distribution functions and nuclear EMC effect in a statistical model

A new and simple statistical approach is performed to calculate the parton distribution functions （PDFs） of the nucleon in terms of light-front kinematic variables.Analytic expressions of x-dependent PDFs are obtained in the whole x region.And thereafter,we treat the temperature T as a parameter of the atomic number A to explain the nuclear EMC effect in the region x ∈ [0.2,0.7].We give the predictions of PDF ratios,and they are very different from those by other models,thus experiments aiming at measuring PDF ratios are suggested to provide a discrimination of different models.     

Polarization effect on the spin symmetry for anti-Lambda spectrum in ^16O＋∧ system

^The polarization effect on the spin symmetry for anti-Lambda spectrum in 16 O＋Λ system has been studied in relativistic mean-field theory.The PK1 effective interaction is used for nucleon-meson couplings and G-parity symmetry with a reduction factor ξ = 0.3 is adopted for anti-Lambda-meson couplings.The energy differences between spin doublets in the anti-Lambda spectrum are around 0.10-0.73 MeV for p Λ state.The dominant components of the Dirac spinor for the anti-Lambda spin doublets are found to be near identical.It indicates that the spin symmetry is still well-conserved against the polarization effect from the valence antiLambda hyperon,which leads to a highly compressed cold nucleus with the central density up to 2 - 3 times of saturated density.     

ATLAS commissioning and early physics of resonance and jet production

As early physics programs with the ATLAS detector,we present J/ψ and Υ production cross section and spin alignment measurements,and the strategy for the jet energy calibration.     

K－p scattering and hyperon excitations in a chiral quark model

A chiral quark-model approach is employed to study theˉ KN scattering at low energies.The processes of Kˉp → Σ 0 π 0,Λπ 0 andˉ K 0 n at P K 800 MeV/c （i.e.the center mass energy W 1.7 GeV） are investigated.The analysis shows that the Λ（1405）S 01 dominates the processes Kˉp → Σ 0 π 0,ˉ K 0 n in the energy region considered here.Around P K 400 MeV/c,the Λ（1520）D 03 is responsible for a strong resonant peak in the cross section of Kˉp → Σ 0 π 0 andˉ K 0 n.To reproduce the data,an unexpectedly large coupling for Λ（1520）D 03 to KN is needed.In contrast,the coupling for Λ（1670）S 01 to KN appears to be weak,which could be due to configuration mixings between Λ（1405）S 01 and Λ（1670）S 01 .By analyzing Kˉ p → Λπ 0,evidences for two low mass S-wave states,Σ（1480）S 11 and Σ（1560）S 11,seem to be available.With these two states,the reaction Kˉp →ˉ K 0 n can also be described well.However,it is difficult to understand the low masses of Σ（1480）S 11 and Σ（1560）S 11 .The s-channel amplitudes for Kˉp → Λπ 0 are also larger than the naive quark model expectations.The non-resonant background contributions,i.e.t-channel and/or u-channel,also play important roles in the explanation of the angular distributions due to amplitude interferences.     

Prospectives of the hadron program in ATLAS

One of the first measurements that will be made at the LHC by ATLAS deals with the properties of inelastic collisions,namely the central charged particle density and transverse momentum distributions.Current predictions of these distributions have large uncertainties in the LHC energy range.We describe the ATLAS minimum bias triggers,designed to select all kind of inelastic interactions,and the performance of the track reconstruction software which was adapted to soft particle track reconstruction.The precision with which the minimum bias distributions can be measured with early data is presented and the uncertainties on the inelastic distributions due to trigger bias is discussed.     

Search for new physics in the B→K^（＊）l^＋l^- decays at BABAR

Based on a data sample of 384 million BB pairs collected with the BABAR detector at the PEP-Ⅱ asymmetric e ＋ e ￣ storage ring,we measure branching fractions,direct CP,isospin and lepton-flavor asymmetries for the rare decays B → K （＊） l ＋ l￣ in two di-lepton mass bins above and below the J/ψ resonance.For the B → K＊ l ＋ l￣ decay,we also measure the K＊ longitudinal polarization fraction and the di-lepton forwardbackward asymmetry.     

Semileptonic bc to cc and bb to bc baryon decays and heavy quark spin symmetry

We study the semileptonic decays of the lowest-lying bc baryons to the lowest-lying cc baryons （Ξ （＊） bc → Ξ （＊） cc and Ω （ ＊） bc → Ω （＊） cc ）,in the limit m b,m c Λ QCD and close to the zero recoil point.The separate heavy quark spin symmetries make it possible to describe all these decays using a single form factor.We also show how these constraints can be used to test the validity of different quark model calculations.bb to bc baryon decays are also discussed.     

Entanglement in a two-qubit Heisenberg XXZ chain with different Dzyaloshinskii-Moriya couplings and an inhomogeneous magnetic field

Ground state entanglement and thermal entanglement of a two-qubit Heisenberg XXZ chain in the presence of the different Dzyaloshinski-Moriya interaction and inhomogeneous magnetic field are investigated.By the concept of concurrence,we find that the inhomogeneity of the magnetic field may make entanglement last for a long time and the critical temperature is dependent on Jz and b.The entanglement can be increased by increasing the temperature in some cases.We also find that the x-component parameter Dx has a higher critical temperature and more entanglement for a certain condition than the z-component parameter Dz.     

Measurement of PV asymmetry in n＋p→d＋γ and γ＋d→n＋p

The measurement of parity-violating （PV） observables in few-nucleon system can shed light on our current understanding of the weak interaction between nucleons.Theoretical models describe the nucleonnucleon weak interaction at low energies use a series of undetermined parameters.Two parity violating measurements have been considered： the capture of polarized slow neutrons on hydrogen （n ＋ p → d ＋ γ） at Los Alamos National Laboratory for first phase and Oka Ridge National Laboratory for second phase and the helicity dependence of the deuteron photodisintegration cross section using circularly polarized photons （γ ＋ d → n ＋ p） at Shanghai Institute of Applied Physics.The goal of both experiments is to constraint the weak meson-nucleon couplings to a precision of 1 ×10^-8 .The introduction of both experiments is presented.     

Determining the strange and antistrange quark distributions of the nucleon

The difference between the strange and antistrange quark distributions,δs（x） = s（x） ˉs（x）,and the combination of light quark sea and strange quark sea,Δ（x） =ˉ d（x） ＋ uˉ（x） s（x） ˉs（x）,are originated from non-perturbative processes and can be calculated using non-perturbative models of the nucleon.We report calculations of δs（x） and Δ（x） using the meson cloud model.Combining our calculations of Δ（x） with relatively well known light antiquark distributions obtained from global analysis of available experimental data,we estimate the total strange sea distributions of the nucleon.     

High pt and photon physics with ALICE at LHC

ALICE,A Large Ion Collider Experiment,is dedicated to study the QCD matter at extreme high temperature and density to understand the Quark Gluon Plasma （QGP） and phase transition.High-transversemomentum photons and neutral mesons from the initial hard scattering of partons can be measured with ALICE calorimeters,PHOS （PHOton Spectrometer） and EMCAL （ElectroMagnetic CALorimeter）.Combing the additional central tracking detectors,the γ-jet and π 0-jet measurements thus can be accessed.These measurements offer us a sensitive tomography probe of the hot-dense medium generated in the heavy ion collisions.In this paper,high p T and photon physics is discussed and the ALICE calorimeters capabilities of high-transverse-momentum neutral mesons and γ-jet measurements are presented.     

Preliminary study of a niobium quarter-wave prototype cavity for a heavy-ion superconducting linac

Superconducting quarter-wave resonators,due to their compactness and their convenient shape for tuning and coupling,are very attractive for low-β beam acceleration.In this paper,two types of cavities with different geometry have been numerically simulated the first type with larger capacitive load in the beam line and the second type of lollipop-shape for 100 MHz,β=0.06 beams then the relative electromagnetic parameters and geometric sizes have been compared.It is found that the second type,whose structural design is optimized with the conical stem and shaping drift-tube,can support the better accelerating performance.At the end of the paper,some structural deformation effects on frequency shifts and appropriate solutions have been discussed.     

A Particle-in-cell scheme of the RFQ in the SSC-Linac

A 52 MHz Radio Frequency Quadrupole （RFQ） linear accelerator （linac） is designed to serve as an initial structure for the SSC-Linac system （injector into Separated Sector Cyclotron）.The designed injection and output energy are 3.5 keV/u and 143 keV/u,respectively.The beam dynamics in this RFQ have been studied using a three-dimensional Particle-In-Cell （PIC） code BEAMPATH.Simulation results show that this RFQ structure is characterized by stable values of beam transmission effciency （at least 95%） for both zerocurrent mode and the space charge dominated regime.The beam accelerated in the RFQ has good quality in both transverse and longitudinal directions,and could easily be accepted by Drift Tube Linac （DTL）.The effect of the vane error and that of the space charge on the beam parameters have been studied as well to define the engineering tolerance for RFQ vane machining and alignment.     

Heavy quark spin symmetry and heavy flavor hadronic molecules

We argue that the heavy quark spin symmetry can lead to important consequences for heavy flavor hadronic molecules.It can be used to predict new heavy flavor hadronic molecules and hence provides a method to identify the nature of some newly observed exotic hadrons.For example,if the Y（4660） were an S-wave ψ f 0 （980） shallow bound state,then the mass,width and line shape of its spin partner are predicted.     

Supersymmetric contributions to B_s → K~-π~＋ decay

Recently,the CDF Collaboration has measured the branching fraction and time-integrated direct CP asymmetry of Bs → K-π＋ decay.The branching ratio is lower than the previous predictions based on QCD factorization.The experimental results favor a large CP asymmetry in Bs → K-π＋ decay while the standard model prediction is very small.We compute the supersymmetry contributions to Bs → K-π＋ decay using the mass insertion method,and find that the LR and RL mass insertions could suppress this branching ratio and increase this direct CP asymmetry well in line with the experimental data.     

Quark-clustering in cold quark matter

Quarks are proposed to be grouped together to make quark-clusters due to the strong interaction in cold quark matter at a few nuclear densities,because a weakly coupling treatment of the interaction between quarks there would be inadequate.Cold quark matter is then conjectured to be in solid state （i.e.,forming a crystal structure） if the inter-cluster potential is deep enough to localize clusters in lattice.Such a solid state of cold quark matter would be very necessary for us to understand different manifestations of pulsar-like compact stars,and could not be ruled by first principles.