Λ■ production in p collis

We describe the production of ΛΛ in pp collisions using a constituent quark model which has been successfully applied to the N N system.     

A-dependence of φ-meson production in p + A collisions

A systematic analysis of the A-dependence of φ-meson production in proton-nucleus collisions is presented. We apply different formalisms for the evaluation of the φ-meson distortion in nuclei and discuss the theoretical uncertainties of the data analysis. The corresponding results are compared to theoretical predictions. We also discuss the interpretation of the extracted results with respect to different observables and provide relations between frequently used definitions. The perspectives of future experiments are evaluated and estimates based on our systematical study are given.     

Parton rescattering effect on particle production in ultra-relativistic p+p collisions

The parton rescattering effect on the charged particle production in ultra-relativistic p+p collisions is studied by the parton and hadron cascade model PACIAE, based on PYTHIA. We have calculated charged particle pseudorapidity density at mid-rapidity and the pseudorapidity distribution in inelastic and non-single diffractive p+p collisions at $\sqrt{s}=200$ , 900, 5500, and 14000 GeV with the PYTHIA and PACIAE models. The calculated results for $\sqrt{s}=900$  GeV are well compared with the ALICE data. Comparing the PYTHIA results (without parton rescattering) with the PACIAE results (with parton rescattering), it turned out that the parton rescattering may play an important role and this effect increases with increasing CMS energy.     

Λ∧ production in pp collis

We describe the production of Λ Λ in pp collisions using a constituent quark model which has been successfully applied to the N N system.     

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.     

d′ production in heavy-ion collisions

The production of d′ dibaryons in heavy-ion collisions due to the elementary process NN → d′π is considered. The NN → d′π cross section is estimated using the vacuum d′ width Γ_d′ ≈ 0.5 MeV extracted from data on the double charge exchange reactions on nuclei. The d′ production rate per single collision of heavy ions is estimated at an incident beam energy of 1 A GeV within the framework of the Quantum Molecular Dynamics transport model. We suggest to analyse the invariant mass spectrum of the NNπ system in order to search for an abundance of events with the invariant mass of the d′ dibaryon. The d′ peak is found to exceed the statistical fluctuations of the background at a 6σ level for 2 × 10⁵ · A central collisions of heavy ions with the atomic number A.     

Jet production in hadronic collisions to0(α s 3 )

We present the full0(α _s ³ ) QCD corrections to jet production within a small opening angle δ at large transverse momenta for all partonic subprocesses. Results for CERN and Tevatron colliders are given with particular emphasis on the sensitivity to renormalization and factorization mass scales.     

ηproduction in proton-nucleus collisions near threshold

The η-meson production in proton-nucleus(pA)collisions near threshold is studied within a relativistic meson-exchange model.The primary production amplitude is presented in the distorted-wave impulse approximation for the nucleus with isospin 0 or [1]by assuming that N*(1535)is excited via a meson exchange and then decays into η and nucleon pair(ηN).Taking 18O and 12C nuclei as examples,we evaluate the production cross sections as a function of the incident proton energy,and analyze the effects of nuclear medium and various meson-exchange contributions.Finally we discuss implications for further experimental studies at the Cooling Storage Ring(CSR)in Lanzhou.     

η production in proton-nucleus collisions near threshold

The η-meson production in proton-nucleus (pA) collisions near threshold is studied within a relativistic meson-exchange model. The primary production amplitude is presented in the distorted-wave impulse approximation for the nucleus with isospin 0 or 1 by assuming that N^*(1535) is excited via a meson exchange and then decays into η and nucleon pair(ηN). Taking ¹⁸O and ¹²C nuclei as examples, we evaluate the production cross sections as a function of the incident proton energy, and analyze the effects of nuclear medium and various meson-exchange contributions. Finally we discuss implications for further     

Double-λ hypernuclear production in high-energy heavy-ion collisions

The production of double- hypernuclei was studied regarding three different mechanisms: (1) coalescence of a nuclear fragment from peripheral collisions and two A particles, (2) coalescence of two A particles, neutrons and protons due to central collisions, and (3) conversion of a hypernucleus. The production probability is estimated for several projectile-target combinations at 5 and 14.5 GeV/nucleon.     

Proton and Λ hyperon production in nucleus-nucleus collisions

Experimental data obtained by the NA35 Collaboration for the difference of the p and \(\bar p\) spectra and the difference of the Λ and \(\bar \Lambda\) spectra (net proton and Λ-hyperon spectra), as well as the inclusive Λ and \(\bar \Lambda\) spectra measured by the NA49, NA57, and STAR Collaborations, are compared with the predictions of the quark-gluon string model. The contribution of string-junction diffusion is calculated, and interaction with nuclear clusters is taken into account along with the corrections for inelastic screening. The level of numerical agreement with experimental data is between 20 and 30%. The predictions for the LHC energy are given.     

Production of Λ-hypernuclei in A(p,K~ )ΛB reactions

The production of Λ-hypernuclei in the A(p,K )ΛB reaction is investigated in the framework of the distorted wave impulse approximation(DWIA). The total cross sections and differential cross sections for various nuclear targets are calculated with an elementary process pN→NKΛ where the additional contributions from the N*(1535) resonance and the final state interaction between p and Λ are included. The dependence of the production cross sections of Λ-hypernuclei on the phenomenological nuclear density and the nucleon number in the target, as well as the distortion effect of the incident proton and outgoing kaon, are also explored. It is shown that the distortion effect tends to decrease the cross sections by a factor of about 3—10. The production cross sections are sensitive to the adopted nuclear density.     

Λ_b~0-baryon production in pp collisions in the general-mass variable-flavour-number scheme,and comparison with CMS and LHCb data

We calculate the next-to-leading-order cross section for the inclusive production ofΛ_(b )baryons in pp collisions in the general-mass variable-flavor-number scheme.We use realistic evolved non-perturbative fragmentation functions obtained from fits to B-meson production in e~+e~-annihilation and compare our results for transversemomentum and rapidity distributions with recent experimental data from the CMS and the LHCb collaborations at the CERN LHC.We find satisfactory agreement in general,with some indication for the need to modify the available fragmentation functions at larger values of the scale variable.     

Study of ππ production in two-photon collisions at Belle

We have measured the cross section for π+π- production in two-photon collisions using a data sample with an integrated luminosity of 85.9 fb-1 collected with the Belle detector. The f0(980) resonance is observed as a peak in the energy spectrum of the cross section. We also report preliminary results for γγ→π0π0 with two-photon center-of-mass energies ranging from 0.6 to 4.0 GeV, based on a 95 fb-1 data sample. We find at least four resonant structures including a peak from f0(980). In addition, there is evidence for Xc0 production. We also make a preliminary discussion of the angular dependence and cross section ratio of γγ→π+π- and γγ→π0π0.     

Anomalous couplings in single Higgs production throughγγ collisions

We show that single Higgs production inγγ collisions through laser backscattering provides the best way to look for New Physics (NP) effects inducing anomalous Higgs couplings. Our analysis is based on the fourdim=6 operators ${\mathcal{O}}_{UB} , {\mathcal{O}}_{UW, } \bar {\mathcal{O}}_{UB} $ , and $\bar {\mathcal{O}}_{UW} $ which describe New Physics effects in this sector. Using the Higgs production rate we establish observability limits for the couplings of the aforementioned operators at a level of 10^?3, which means establishing lower bounds on the scale of NP of the order 30 to 200 TeV. Higgs branching ratios, especially the ratio Γ(H→γγ)/Γ(H→γZ), are shown to provide powerful ways to disentangle the effects of the various operators.     

Study of ππ production in two-photon collisions at Belle

We have measured the cross section for π⁺π^－ production in two-photon collisions using a data sample with an integrated luminosity of 85.9fb^－1 collected with the Belle detector. The f₀(980) resonance is observed as a peak in the energy spectrum of the cross section. We also report preliminary results for γγ→π⁰π⁰ with two-photon center-of-mass energies ranging from 0.6 to 4.0GeV, based on a 95fb^－1 data sample. We find at least four resonant structures including a peak from f₀(980). In addition, there is evidence for χ_c0 production. We also make a preliminary discussion of the angular dependence and cross section ratio of γγ→π⁺π^－ and γγ→π⁰π⁰.