pp final state interaction in J/ψ →γpp

The phenomenon of the near ppˉ-threshold enhancement observed in the J/ψ→γ pp decay is studied by using the enhancement factor method with a simpler one-pion-exchange potential between p and p. The Jost function caused by the mentioned potential is perturbatively calculated in the zero-th order approximation, and the corresponding enhancement factor is obtained. It is found that such a final state interaction offers an important contribution to the decay width near the ppˉ-threshold, although it is not large enough. To explain the decay data, a phenomenological factor G(p) with the form of 285500/(m 2 π + p 2 ) should be introduced. A further calculation including the p-dependent bare T -matrix, a more realistic N ˉ N potential and the contribution from the higher-order wave functions would provide a better understanding of the decay data and even the existence of the baryonium ppˉ. The near ppˉ-threshold behavior of the decay width in the J/ψ→π 0 pp process is also discussed.     

N＊（1535） contribution in pp →ppη＇ and pn →dφ

In an effective Lagrangian model we find that the N＊（1535） resonance contribution might be important to the interpretation of the present data of the pp →ppη＇ and pn →dφ reactions. The strong coupling strength of N＊ （1535） to η＇ and φ are indicated, and the possible implication to the intrinsic component of N＊（1535） is explored. These results may provide hints to the real origin of the OZI rule violation. It is stressed that further measurements could be performed at China. the Cooling Storage Ring （CSR） at Lanzhou of     

Near-threshold η production in pp collisions

We study near-threshold η meson production in pp collisions within an effective Lagrangian approach combined with the isobar model, by allowing for the various intermediate nucleon resonances due to the π, η, and ρ-meson exchanges. It is shown that the ρ-meson exchange is the dominant excitation mechanism for these resonances,and the contribution from the N*(1720) is dominant. The total cross section data can be reasonably reproduced,and the anisotropic angular distributions of the emitted η meson are consistent with experimental measurements.Besides, the invariant mass spectra of pp and pη explain the data well at excess energy of 15 Me V, and are basically consistent with the data at excess energy of 40 Me V. However, our model calculations cannot reasonably account for the two-peak structure in the pη distribution at excess energies of 57 and 72 Me V, which suggests that a more complicated mechanism is needed at higher energy region.     

Study on the Effects of the Light CP-odd Higgs via the Leptonic Decays of Pseudoscalar Mesons

To explain the anomalously large decay rate of Σ+→ p+μ+μ- , it was proposed that a new mechanism where a light CP-odd pseudoscalar boson of mA10 = 214.3 MeV makes a crucial contribution. Later, some authors have studied the transition π0→e+e- and Υ→γA10 in terms of the same mechanism and their result indicates that with the suggested mass one cannot fit the data. This discrepancy might be caused by experimental error of Σ+→p+μ+μ- because there were only a few events. Whether the mechanism is a reasonable one motivates us to investigate the transitions π0→e+e-; η(η′) →μ+μ- ; ηc→μ+μ- ;ηb→τ+τ- within the same framework. It is noted that for π0→e+e-, the standard model (SM) prediction is smaller than the data, whereas the experimental central value of η→μ+μ- is also above the SM prediction. It means that there should be extra contributions from other mechanisms and the contribution of A10 may be a possible one. Theoretically calculating the branching ratios of the concerned modes, we would check if we can obtain a universal mass for A10 which reconcile the theoretical predictions and data for all the modes. Unfortunately, we find that it is impossible to have such a mass with the same coupling |ge|. Therefore we conclude that the phenomenology does not favor such a light A10 , even though a small window is still open.     

High-frequency gravitational waves having large spectral densities and their electromagnetic response

Various cosmology models, brane oscillation scenarios, interaction of interstellar plasma with intense electromagnetic radiation, and even high-energy physics experiments （e.g., Large Hadron Collider （LHC）） all predict high frequency gravitational waves （HFGWs, i.e., high-energy gravitons） in the microwave band and higher frequency region, and some of them have large energy densities. Electromagnetic （EM） detection to such HFGWs would be suitable due to very high frequencies and large energy densities of the HFGWs. We review several typical EM detection schemes, i.e., inverse Gertsenshtein effect （G-effect）, coupling of the inverse G effect with a coherent EM wave, coupling of planar superconducting open cavity with a static magnetic field, cylindrical superconducting closed cavity, and the EM sychro-resonance system, and discuss related minimal detectable amplitudes and sensitivities. Furthermore, we give some new ideas and improvement ways enhancing the possibility of measuring the HFGWs. It is shown that there is still a large room for improvement for those schemes to approach and even reach up the requirement of detection of HFGWs expected by the cosmological models and high-energy astrophysical process.     

Time-like proton form factor measurement with PANDA

The electromagnetic probe is an excellent tool to investigate the structure of the nucleon. The nearly 4π detector PANDA, will allow to make a precise determination of the electromagnetic form factors of the proton in the time-like region with unprecedented precision. In the one-photon exchange approximation, the center of mass unpolarized differential cross section of the reaction pp → e＋e- is a linear combination of the squared moduli of the electric GE and magnetic GM proton form factors. The precise measurement of the angular distribution over almost full angular range then directly gives these quantities. At present only two experiments have provided the ratio R=｜ GE｜/｜GM｜ but with large statistical uncertainties. It is shown that with strict PID cuts and a kinematic fit, the dominant background, pp→π＋π-, can be supressed to much less than 1% of the signal, without affecting the extraction of the ratio R. PANDA will therefore offer a unique opportunity to measure the ratio with a precision ranging from 〈1% at low q2 up to 30 % for q2 = 14 （GeV/c）2.     

Two-photon exchange properties in to proton electromagnetic time-like region

The contributions of two-photon exchange in the process e＋ ＋ e-→ p ＋ p including N and △ intermediate states are estimated in a simple hadronic model. The corrections to the unpolarized cross section as well as to the polarized observables Px and Px are evaluated. The results show the corrections to unpolarized cross section are small and the angle dependence becomes weak at small s after considering the N and △（1232） contributions simultaneously, while the correction to Px is enhanced.     

Constituent quark number scaling from strange hadron spectra in pp collisions at ■=13 TeV

We show that the p_T spectra of Ω~- and φ at midrapidity in the inelastic events in pp collisions at ■=13 TeV exhibit a constituent quark number scaling property,which is a clear signal of quark combination mechanism at hadronization.We use a quark combination model with equal velocity combination approximation to systematically study the production of identified hadrons in pp collisions at ■=13 TeV.The midrapidity spectra for protons,∧,Ξ~-,Ω~-,φ and K~* in the inelastic events are simultaneously fitted by the model.The multiplicity dependence of the yields of these hadrons are also well understood.The strong p_T dependence of the p/φ ratio is well explained by the model,which further suggests that the production of two hadrons with similar masses is determined by their quark content at hadronization.The p_T spectra of strange hadrons at midrapidity in different multiplicity classes in pp collisions at ■=13 TeV are predicted for further tests of the model.The midrapidity p_T spectra of soft (p_T 2 GeV/c)strange quarks and up/down quarks at hadronization in pp collisions at ■=13 TeV are extracted.     

Theoretical Prediction with Monte Carlo Simulation for pp → nK^＋∑^＋ through △^＋＋＊ Resonance Production

The pp → nK^＋E^＋ reaction is a very good isospin 3/2 filter for studying △^＋＋＊ decaying to K^＋E^＋. The proton beam experiment with a scheduled 4π hadron detector at Lanzhou Cooler Storage Ring （CSR） will make the study of this reaction possible. Here, based on very limited available knowledge on the relevant ingredients for this reaction, we give theoretical prediction with Monte Carlo simulation for various observables for this reaction. This could serve as a reference for building the scheduled hadron detector and for identifying new physics in the following-on experiments at CSR.     

Pomeron-Quark Coupling from Charge Conjugation Invariance

Based on the charge conjugation invariance and the vazuum property of the Pomeron, we point out that the commonly used vector vertex of the Pomeron coupling to quarkis incorrect since it contradicts with the Pomeron property. We also claim that the soft Pomeron could be a tensor glueball ξ（2230） with quantum numbers I^GJ^PC = 0^＋2^＋＋ and total decay width Гtot ≌ 100 MeV, which lies on the soft Pomeron trajectory αp = 1.08＋ 0.20t. Therefore, the coupling vertex of the soft Pomeron to quark should be tensorial which is invariant under the charge conjugation and can explaIn why the inadequate vector coupling, γ^μ, of the soft Pomeron to quark is successful in dealing with Pomeron physics.     

QGP tomography with photon tagged jets in ALICE

γ＋jet events provide a tomographic measurement of the medium formed in heavy ion collisions at LHC energies.Tagging events with a well identified high p T direct photon and measuring the correlation distribution of hadrons emitted oppositely to the photon in ALICE,allows us to determine,with a good approximation,both the jet fragmentation function and the back-to-back azimuthal alignment of the direct photon and the jet.Comparing these two observables measured in pp collisions with the ones measured in AA collisions will reveal the modifications of the jet structure induced by the medium formed in AA collisions and consequently will infer the medium properties.     

Prospects of Bc Mesons at the Compact Muon Solenoid

The results of two Monte Carlo generators for production of Bc mesons in pp collisions are compared at the large hadron collider energy √s = 14 TeV. In the study, the produced Bc mesons were forced to decay into the final states Bslv, Bsπ, J/ψlv, and J/ψπ. We have estimated that about 104 decays of Bc are expected to be recorded during the first year of the CMS running with a lepton trigger. Many Bc studies can be carried out by using these events with a statistical error at the level of 10^-2.     

Feasibility study of a J/ψ cross section measurement with early CMS data

We report the methods and plans for measuring the differential cross section of J/ψ→μ^＋μ^- production, using data to be collected in the first LHC run by the CMS detector. Making use of the large B-hadron lifetime, we show how to separate the promptly produced J/ψ’s from those coming from B-hadron decays. Since the J/ψ production cross section is expected to be large, the analysis should be viable with relatively small data sets, that will become available early in the startup of the LHC. We also address effects of a non-perfect detector alignment, as well as systematic uncertainties. About 70 thousand J/ψ decays are reconstructed from Monte Carlo data, which corresponds to an integrated luminosity of 3 pb^-1 in 14 TeV collisions, in the range of pT^J/ ψbetween 5 and 40 GeV/c. The precision of the result is limited by systematic uncertainties, and is at the 15% level.     

Comparative study of the forward and backward methods for calculating jet properties in pp collisions at s~(1/2)=7 TeV

We propose a forward method based on PYTHIA6.4 to study the jet properties in ultra-relativistic pp collisions.In the forward method,the partonic initial states are first generated with PYTHIA6.4 and then hadronized in the Lund string fragmentation model,and finally the hadronic jets are constructed from the created hadrons.Jet properties calculated with the forward method for pp collisions at √s=7 TeV are comparable to those calculated with the usual anti-kt algorithm(backward method)in PYTHIA6.4.The comparison between the backward and forward methods may contribute to the understanding of the partonic origin of jets in the backward method.     

Study of K~*(892)~0 and ?(1020) meson production in proton–proton and Pb–Pb collisions at ■=2.76 TeV

In this paper, we describe a study of charged particle yield as a function of pTfor K~*(892)~0 and ?(1020) mesons in proton–proton(pp) and Pb–Pb collisions at ■=?2.76 Te V in the central rapidity region of |y|0.5, in a pTrange of ?pT15 Ge V c~(-1) in pp collisions and in a pT range of 0??pT??20 Ge V c~(-1) in Pb-Pb collisions. We also investigated a very important ratio,the nuclear modification factor, to study the effects of the medium in the most central region, i.e.0%–5% centrality. For data simulation, we used the EPOS-LHC and EPOS-1.99 models. To check the validity of these models' simulations, we compared the data obtained from these Monte Carlo simulation programs with ALICE experimental data for ■=?2.76 Te V. It was concluded that the models' predictions for the ?-meson in pp and for the most central Pb-Pb collisions disagreed with the ALICE data, and that the difference increased with pT. This may be connected with the essential role of collective parton behaviors which could not have been taken into account by the models. For K~(*0) mesons, both programs gave almost the same predictions,and with pTin the interval pT??3 Ge V c~(-1), the predictions were very close to the experimental data. Both models gave higher predictions for the soft pTinterval and lower predictions for the hard interactions. The values of the RAAdistributions were lower than unity and both models were very close to the ALICE data. It is very interesting that the models were not able to describe the pTdistributions, but they gave good predictions for their ratios. This may possibly be due to parton collective behaviors. We observed some additional suppression of K~(*0) at low values of pT with respect to f-mesons, which may be related to the role of the masses of the particles in soft interactions. The rising trend for R_(AA) in the region from pT=?10 Ge V c~(-1) to 20 Ge V c~(-1) observed by the ALICE experiment was absent for the f-mesons.     

One-Dimensional Two-Component Bosons with Attractive Interaction

The Bethe-ansatz method is used to solve one-dimensional two-component bosons with a δ-function potential considering the negative coupling constant part. With the string hypothesis of Minoru Takahashi, the features of the ground state and low-lying excited states of this model are discussed explicitly by analytical and numerical methods. Especially for a N = 2 system, the two bosons being pairs is obvious, and the ground state which is independent of the coupling constant should be ferromagnetic.     

Large angle radiation effect on jet measurement in pp collisions at s~(1/2)=7 TeV at the LHC

Jet measurement is an ideal probe to explore the properties of the hot dense matter created in ultrarelativistic heavy-ion collisions. Recent results at the LHC show that large angle radiation is non-negligible, but the mechanisms and phenomenology of large angle radiation are still unclear and hotly debated. Considering the coexistence and competition of different physics mechanisms qualitatively, it is assumed that the radiation angle is enhanced randomly over a wide range based on the collinear approximation. Its effects on di-jet momentum imbalance, jet fragmentation function and jet shape are studied in pp collisions at 7 TeV. The results show that di-jet asymmetry is insensitive to large angle radiation, while jet shape and jet fragmentation functions are more sensitive and could explain experimental data well. We conclude that de-collimated radiation cannot be ignored for soft jets,and there is a contribution from large angle radiation(φ 0.7) of about 8%, which is significant for jet intrinsic structure measurement at p T,jet 80 GeV/c.     

Pion Production in Heavy-Ion Collisions in the 1 A GeV Region

Within the framework of the improved isospin dependent quantum molecular dynamics （ImIQMD） model, pion emission in heavy-ion collisions in the region 1 A GeV is investigated systematically, in which the pion is considered to be mainly produced by the decay of resonances △（1232） and N^＊（1440）. The in-medium dependence and Coulomb effects of pion production are included in the calculation. Total pion multiplicity and π^-/π^＋ yields are calculated for the reaction ^197Au＋^197Au in central collisions for selected Skyrme parameters SkP, SLy6, Ska, SⅢ and compared with the measured data of the FOPI collaboration.     

NNLO QCD predictions of electron charge asymmetry for inclusive pp→W+X production in forward region at 13 and 14 TeV

This paper presents perturbative QCD predictions of the electron charge asymmetry for inclusive W~±X→e~±v+X production in proton-proton(pp) collisions.Perturbative QCD calculations are performed at nextto-next-to-leading order(NNLO) accuracy using different parton distribution function(PDF) models at 8,13,and 14 TeV center-of-mass energies of CERN LHC pp collisions.NNLO calculations are performed for electrons with transverse momenta above 20 GeV in the forward electron pseudorapidity region 2.0 ≤η_e≤4.25.NNLO predictions are first compared at 8 TeV with the measurements of the LHCb experiment at the LHC for the W~+/W~-cross section ratio and charge asymmetry distributions.The 8 TeV predictions using NNPDF3.1,CT14,and MMHT2014 PDF sets are reported to be in good agreement with the LHCb data for the entire η_e region,justifying the extension of the calculations to 13 and 14 TeV energies.The charge asymmetry predictions at NNLO accuracy are reported in the forward η_e bins at 13 and 14 TeV and compared among NNPDF3.1,CT14,and MMHT2014 PDF sets.Overall,the predicted W~± differential cross-section and charge asymmetry distributions based on different PDF sets are found to be consistent with each other for the entire η_e region.The charge asymmetry distributions are shown to be more sensitive to discriminate among different PDF models in terms of the 14 TeV predictions.