Hadrinoc production of χ c -nesons at LHC

Hadronic production of P-wave charmonium states χ _cJ in hadronic interaction is considered. Using the experimental results of CDF and LHCb collaborations, we show, that contributions of color singlet components are dominant. As for the color octet mechanism, then we show, that contributions from P-wave states can also be observed, while the contribution from S-wave is negligible. The best experimental observables that give information about relative importance of color-singlet and color-octet components are the ratios χ _c2/χ _c1 and χ _c 0/χ _c1.     

Formation of a 4c tetraquark in J/ψ-meson pair production at LHC

Cross sections for J??-meson pair production in proton-proton interaction at the c.m. collision energy of $\sqrt s = 7$ TeV were theoretically predicted under conditions of various kinematical cuts. The possible contribution to this process from the decays of 4c tetraquarks, new hypothetic particles consisting of two valence c quarks and two valence $\bar c$ antiquarks, was studied. It is shown that at least one such state (tensor 4c tetraquark) can in principle be observed experimentally under conditions of the LNCb experiment.     

DJpsiFDC：an event generator for the process gg→J/ψJ/ψ at the LHC

DJpsiFDC is an event generator package for the process gg→J/ψJ/ψ. It generates events for primary leading-order 2→2 processes. The package could generate a Les Houches Event (LHE) document and this could easily be embedded into detector simulation software frameworks. The package is produced in Fortran code.     

DJpsiFDC:an event generator for the process gg→J/ψJ/ψat the LHC

DJpsiFDC is an event generator package for the process gg→J/ψJ/ψ. It generates events for primary leading-order 2 → 2 processes. The package could generate a Les Houches Event (LHE) document and this could easily be embedded into detector simulation software frameworks. The package is produced in Fortran code.     

Observation of Cabibbo-suppressed and W-exchange Λ c + baryon decays

We present measurements of the Cabibbo-suppressed decays Λ _c ⁺→Λ ⁰ K ⁺ and Λ _c ⁺→Σ ⁰ K ⁺ (both first observations), Λ _c ⁺→Σ ⁺ K ⁺ π ⁻ (seen with large statistics for the first time), Λ _c ⁺→pK ⁺ K ⁻ and Λ _c ⁺→pφ (measured with improved accuracy). Improved branching ratio measurements for the decays Λ _c ⁺→Σ ⁺ K ⁺ K ⁻ and Λ _c ⁺→Σ ⁺ φ, which are attributed to W-exchange diagrams, are shown. We also present the first evidence for Λ _c ⁺→Ξ(1690)⁰ K ⁺ and set an upper limit on the non-resonant decay Λ _c ⁺→Σ ⁺ K ⁺ K ⁻. This analysis was performed using 32.6 fb⁻¹ of data collected by the Belle detector at the asymmetric e ⁺ e ⁻ collider KEKB.     

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.     

A new search for the doubly charmed baryon ■ at the LHC

The standard quark model is capable of predicting the existence of doubly heavy baryons.Similar to doubly heavy mesons,doubly heavy baryons may allow the QCD-inspired potential model,the nonrelativistic QCD(NRQCD)factorization theory[1],etc.,to work on them well,while serving as a fruitful“laboratory”for testing these theories when a greatly enough collection of relevant data is available.Many attempts have been made to observe doubly heavy baryons,yet none of them succeeded due to the difficulties in producing such baryons either at the e^+e^- colliders or at the hadronic colliders.Noticeably,the running of the large hadronic collider(LHC)with a large centre-of-mass protonproton collision energy and a much higher luminosity provides a good opportunity for experimentalists to realize the aforementioned observation.     

Determinations of $$|V_{cb}|$$ and $$|V_{ub}|$$|Vub| from baryonic $$\Lambda _b$$Λb decays

We present the first attempt to extract \(|V_{cb}|\) from the \(\Lambda _b\rightarrow \Lambda _c^+\ell \bar{\nu }_\ell \) decay without relying on \(|V_{ub}|\) inputs from the B meson decays. Meanwhile, the hadronic \(\Lambda _b\rightarrow \Lambda _c M_{(c)}\) decays with \(M=(\pi ^-,K^-)\) and \(M_c=(D^-,D^-_s)\) measured with high precisions are involved in the extraction. Explicitly, we find that \(|V_{cb}|=(44.6\pm 3.2)\times 10^{-3}\), agreeing with the value of \((42.11\pm 0.74)\times 10^{-3}\) from the inclusive \(B\rightarrow X_c\ell \bar{\nu }_\ell \) decays. Furthermore, based on the most recent ratio of \(|V_{ub}|/|V_{cb}|\) from the exclusive modes, we obtain \(|V_{ub}|=(4.3\pm 0.4)\times 10^{-3}\), which is close to the value of \((4.49\pm 0.24)\times 10^{-3}\) from the inclusive \(B\rightarrow X_u\ell \bar{\nu }_\ell \) decays. We conclude that our determinations of \(|V_{cb}|\) and \(|V_{ub}|\) favor the corresponding inclusive extractions in the B decays.     

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.     

Prospects for searching the η→e+e- rare decay at the CSR

We study the possibility of searching the η→e+e- rare decay on the Cooling Storage Ring (CSR) at Lanzhou. The main features of the proposed Internal Target Experiment (ITE) and External Target Facility (ETF) are included in the Monte Carlo simulation. Both the beam condition at the CSR and the major physics backgrounds are carefully taken into account. We conclude that the ITE is more suitable for such a study due to better detector acceptance and higher beam density. At the maximum designed luminosity (1034cm-2s-1 ), η→e+e- events can be collected every～400 seconds at the CSR. With a mass resolution of 1 MeV, the expected signal-to-background (S/B) ratio is around 1.     

Prospects for searching the η→e+e- rare decay at the CSR

We study the possibility of searching the η→e⁺e^- rare decay on the Cooling Storage Ring (CSR) at Lanzhou. The main features of the proposed Internal Target Experiment (ITE) and External Target Facility (ETF) are included in the Monte Carlo simulation. Both the beam condition at the CSR and the major physics backgrounds are carefully taken into account. We conclude that the ITE is more suitable for such a study due to better detector acceptance and higher beam density. At the maximum designed luminosity (10³⁴ cm^-2s^-1), η→e⁺e^- events can be collected every ~400 seconds at the CSR. With a mass resolution of 1 MeV, the expected signal-to-background (S/B) ratio is around 1.     

Determination of the number of J/ψ events with inclusive J/ψ decays

A measurement of the number of J/ψ events collected with the BESⅢ detector in 2009 and 2012 is performed using inclusive decays of the J/ψ. The number of J/ψ events taken in 2009 is recalculated to be(223.7±1.4)×10~6, which is in good agreement with the previous measurement, but with significantly improved precision due to improvements in the BESⅢ software. The number of J/ψ events taken in 2012 is determined to be(1086.9±6.0)×10~6. In total, the number of J/ψ events collected with the BESⅢ detector is measured to be(1310.6±7.0)×106, where the uncertainty is dominated by systematic effects and the statistical uncertainty is negligible.     

Properties of the coupling constants of J/ψ→VP decays

Based on the branching fractions of J/ψ→VP from different experiments, we investigate the properties of the coupling constants of J/ψ→VP decays using a model-dependent approach. We find that the octet coupling constant, g8, of strong interaction is about twice larger than that of the singlet coupling constant g₁; the electromag- netic breaking parameters g_Eⁱ are larger than the mass breaking parameters g_Mⁱ, moreover, the three parameters of the electromagnetic effect are about equal, but the three parameters of the mass effect are obviously different and their uncertainties are also large; and the phase angle between strong and electromagnetic interactions is in the range of 70°-80°. It deepens our understanding of the coupling constant of J/ψ→VP decays.     

A Study of the Standard Model Higgs Boson in the H → WW* → ��ν��ν Decay Channel in the ATLAS Experiment at the LHC

Physics of Atomic Nuclei - The authors within the Higgs Boson Working Group of the ATLAS experiment at the LHC performed an analysis of events with two leptons and two hadron jets to study Standard...     

Production of γγ+2 jets from double parton scattering in proton-proton collisions at the LHC

Cross sections for the production of pairs of photons plus two additional jets produced from double parton scattering in high-energy proton-proton collisions at the LHC are calculated for the first time.The estimates are based on the theoretical perturbative QCD predictions for the productions of γγ at next-to-next-to-leading-order,jet+jet and γ+jet at next-to-leading-order,for their corresponding single-scattering cross sections.The cross sections and expected event rates for γγ+2 jets from double parton scattering,after typical acceptance and selections,are given for proton-proton collisions with the collision energy s~(1/2)=13 TeV and integrated luminosity of 100 fb~(-1) planned for the following years,and also s~(1/2)=14 TeV with 3000 fb~(-1) of integrated luminosity as the LHC design.     

Searching for high speed long-lived charged massive particles at the LHC

The conventional way to search for long-lived CHArged Massive Particles (CHAMPs) is to identify slow (small β) tracks using delayed time of flight and high ionization energy loss. But at the 7–14 TeV center of mass energy of the LHC, a CHAMP may be highly boosted (high β) and therefore look more like a minimum ionizing particle, while for high momentum muons (?500 GeV/c) the radiative effect dominates energy deposition. This suggests a new strategy to search for CHAMPs at the LHC. Using energy deposition from different detector components, we construct a boosted decision tree discriminant to separate high momentum CHAMPs from high momentum muons. This method increases substantially the CHAMP discovery potential and it can be used to distinguish possible di-CHAMP or CHAMP–muon resonance models from di-muon resonance models. We illustrate the new method using a mGMSB model and a recently proposed di-CHAMP model and we give updated CHAMP mass limits for these two models using the results from a recent CDF CHAMP search.     

Search for Z’ → WW at LHC with the ATLAS detector

The potential for measuring the Z‘WW coupling with the ATLAS detector at the LHC is investigated under conditions of low and high luminosity. It is estimated that detection of the decay channel Z’ → WW → lν _l jj is possible with 300 fb ⁻¹, for a Z’ boson with sequential model couplings and with a mass up to 2.2 TeV.