A possible signature of new physics at BES-Ⅲ

The recent observations of the purely leptonic decay Ds＋→μ＋νμ and τ＋ντ at CLEO-c and B factory may allow a possible contribution from a charged Higgs boson. One such measurement of the decay constant fD. differs from the most precise unquenched lattice QCD calculation by a level of 4 σ. Meanwhile, the measured ratio, BR（Ds＋→μ＋νμ）/BR（D＋→μ＋νμ）, is larger than the standard model prediction at a 2.0σ level. We discuss that the precise measurement of the ratio BR（Ds＋→μ＋νμ）/BR（D＋→μ＋νμ） at BES-Ⅲ will shed light on the presence of new intermediate particles by comparing the data with the theoretical predictions, especially, the predictions of high precise unquenched lattice QCD calculations.     

Decay constants of pseudoscalar and vector mesons with improved holographic wavefunction

We calculate the decay constants of light and heavy-light pseudoscalar and vector mesons with improved soft-wall holographic wavefuntions,which take into account the effects of both quark masses and dynamical spins.We find that the predicted decay constants,especially for the ratio f V/f P,based on light-front holographic QCD,can be significantly improved,once the dynamical spin effects are taken into account by introducing the helicity-dependent wavefunctions.We also perform detailed χ~2 analyses for the holographic parameters(i.e.the mass-scale parameterκ and the quark masses),by confronting our predictions with the data for the charged-meson decay constants and the meson spectra.The fitted values for these parameters are generally in agreement with those obtained by fitting to the Regge trajectories.At the same time,most of our results for the decay constants and their ratios agree with the data as well as the predictions based on lattice QCD and QCD sum rule approaches,with only a few exceptions observed.     

Search for the doubly charmed baryon ?_(cc)~+

A search for the doubly charmed baryon ?_(cc)~+ with the decay mode ?_(cc)~+→Ξ_c~+K~-π~+ is performed using proton-proton collision data at a centre-of-mass energy of 13 TeV collected by the LHCb experiment from 2016 to 2018, corresponding to an integrated luminosity of 5.4 fb~(-1). No significant signal is observed within the invariant mass range of 3.6 to 4.0 GeV/c~2. Upper limits are set on the ratio R of the production cross-section times the total branching fraction of the ?_(cc)~+→Ξ_c~+K~-π~+ decay with respect to the Ξ_(cc)~(++)→Λ_c~+K~-π~+π~+ decay. Upper limits at 95% credibility level for R in the range 0.005 to 0.11 are obtained for diferent hypotheses on the ?_(cc)~+ mass and lifetime in the rapidity range from 2.0 to 4.5 and transverse momentum range from 4 to 15 GeV/c.     

Effects of a Family Non-universal Z' Boson in B_d → μ~+μ~-and B~-→ π~-μ~+μ~-,ρ~-μ~+μ~-Decays

Motivated by the recently updated experimental measurement on Bˉd →μ+μ and B →πμ+μ decays by CDF and Belle collaborations,we revisit these decays,as well as B →ρμ+μ decay,within the Standard Model,and evaluate the effects of a family non-universal Z' boson.Under the constraint from B(B →πμ+μ),we find the ranges of the Z' couplings SμLμR 5.2 × 10 2 or DμLμR 8.1 × 10 2 are excluded.Within the allowed Z' parameters spaces,comparing with the SM predictions,we find that B(Bˉd →μ+μ),B(B →πμ+μ),and B(B →ρμ+μ) could be enhanced by a factor about 226%,245%,and 254%,respectively,by Z' contributions.However,they are hardly to be reduced.Furthermore,the zero crossing in the normalized forward-backward asymmetry spectrum of B →ρμ+μ decay at low dimuon mass always exists.     

Calibration of Membrane Viscosity of the Reconstituted Vesicles by Measurement of the Rotational DIffusion of Bacteriorhodopsin

Membrane viscosity of the reconstituted vesicles was calibrated by rotational diffusion of bacteriorhodopin(BR) in dimyristoylphosphatidylcholine(DMPC) and egg phosphatidylcholine(PC) vesicles.Rotational diffusion of BR in the vesicles was measured by flash-induced absorption anisotropy decay.BR was,for the first time ,reconstituted successfully into DMPC and egg PC vesicles,From the measurement of flash-induced absorption anisotropy decay of BR,the value of rotational diffusion coefficient D was obtained from each curve fitting by a global fitting procedure and ,in turn,membrane viscosity η was estimated from D.The results have shown that membrane viscosity is temperature-dependent,It was decreased as temperature increased,but a transition occurred in the region of the respective phase transition of DMPC and egg PC,respectively,The decrease of η was fast near the phase transition for DMPC and egg PC.Few effects of lipid/BR ratio and glycerol or sucrose in suspension medium on membrane viscosity were found.     

Rare semileptonic decays of heavy mesons in the heavy quark limit

We study the branching ratios of D+→D0e+ν,DS+→D0e+ν,BS0→B+e-ν,DS+→D+e-e+ and BS0→B0e-e+ rare semileptonic decay processes,which are induced by decays of light quarks,the heavy quarks remain unchanged.The branching ratios of these decay processes are estimated in the heavy quark limit and with SU(3) flavor symmetry.We find that the decay rates are very tiny in the framework of the Standard Model.We also estimate the sensitivities of the measurements of these rare decays at the future experiments,such as BES-Ⅲ,super-B and LHC-b.Observations of these decays may shed some light on new physics beyond the standard model.     

QCD Approach to B →Dπ Decays and CP Violation

The branching ratios and CP violations of the B →Dπ decays, including both the color-allowed and the color-suppressed modes, are investigated in detail within QCD framework by considering all diagrams that lead to three effective currents of two quarks. An intrinsic mass scale as a dynamical gluon mass is introduced to treat the infrared divergence caused by the soft collinear approximation in the endpoint regions, and the Cutkosky rule is adopted to deal with a physical-region singularity of the on mass-shell quark propagators. When the dynamical gluon mass μg is regarded as a universal sca/e, it is extracted to be around μg = 440 MeV from one of the well-measured B →Dπ decay modes. The resulting predictions for all branching ratios are in agreement with the current experimental measurements. As these decays have no penguin contributions, there are no direct CP asymmetries. Due to interference between the Cabibbo-suppressed and the Cabibbo-favored amplitudes, mixing-induced CP violations are predicted in the B →D^±π^±↓ decays to be consistent with the experimental data at 1-σ level. More precise measurements will be helpful to extracting weak angle 2β＋γ.     

Effects of vector leptoquarks onΛb→Λ,lv^-l decay

Experimental data on R(D⁺).R(K⁺),and R(J/ψ),provided by different collaborations,show sizable deviations from the standard model predictions.To describe these anomalies,many new physics scenarios have been proposed.One of them is the leptoquark model,which introduces the simultaneous coupling of vector and scalar leptoquarks to quarks and leptons.To look for similar possible anomalies in the baryonic sector,we investigate the effects of a vector leptoquark U3(3,3,2/3)on various physical quantities related to the tree-levelΛb→Λclv^-l decays(l=u,t),which proceed via b→c l v^-l transiti ons at the quark level.We calculate the differential branching ratio,forward-backward asymmetry,and longitudinal polarizations of leptons and Ac baryons at theμandτlepton channels in the leptoquark model and compare their behavior to the predictions of the SM in terms of q^2.In the calculations,we use the form factors calculated in full QCD as the main input and account for all errors coming from the form factors and model parameters.We observe that at theτchanneL the Ra fit solution to data related to the leptoquark model sweeps some regions out of the SM band;nevertheless,the fit has a considerable intersection with the SM predictions.The Rr type solution gives roughly the same results as the SM on DBR(q^2)-q^2.At theμchannel.the leptoquark model gives results that are consistent with the SM predictions and existing experimental data on the behavior of DBR(q^2)with respect to q^2.Concerning the q^2 behavior of the AFB(q^2),the two types of fits forτand the predictions at the“channel in the leptoquark model give exactly the same results as the SM.We also investigate the behavior of the parameter R(q^2)with respect to q^2 and the value of R(Λc)in both the vector leptoquark and SM models.Both fit solutions lead to results that deviate considerably from the SM predictions for R(q^2)-q^2 and R(Ac).Future experimental data on R(q^2)-q^2 and RC made available by measurements of theΛb→Λcτv^-τchannel,will be particularly helpful.Any experimental deviations from the SM predictions in this channel would emphasize the im porta nee of tree-level hadronic weak tran sitions as good probes of new physics effects beyond the SM.     

Semileptonic decays B/Bs→(D?,D?s)lνl in the PQCD approach with the lattice QCD input

We study the semileptonic B/Bs→(D^?,D^?s)lνl decays in the framework of the Standard Model(SM),by employing the perturbative QCD(PQCD)factorization formalism combined with the lattice QCD input for the relevant transition form factors.We calculate the branching ratios B(B(s)→D^?(s)lνl)with l=(e,μ,τ),the ratios of the branching fractions R(D^?)and R(D^?s),and the physical observables Pτ(D^?(s)),FL(D?(s))and AFB(τ).The“PQCD+Lattice”predictions for B(B→D^?lνl)and R(D^?)agree with the available experimental measurements within errors.For the ratios R(Ds)and R(D^?s),the"PQCD+Lattice"predictions agree with the other predictions.For Pτ(D^?)and FL(D^?),our theoretical predictions agree with the measured values within errors.Our theoretical predictions of the semileptonic B/Bs decays considered could be tested in the near future by the LHCb and Belle II experiments.     

An investigation into the lepton flavor changing neutral current at a Z-factory

The potential for detecting the lepton flavor changing neutral current (LFCNC) via the Z → eτ rare decay at a Z-factory is investigated.Practicable event selection strategies are designed to increase signal significance over SM contributions.Assuming no apparent deviation from SM predictions,one can conclude that the most general model-independent LFCNC effective form factors would be constrained at an unprecedent level,and accordingly a 3-order improvement from LEP1 measurements on the upper limit of BR(Z → eτ) could be achieved,as precisely as 10-8 with 100 fb-1 at Z-factory.     

Uncertainty of parton distribution functions due to physical observables in a global analysis

The recent measurement of the differential γ + c-jet cross section, performed at the Tevatron collider in Run II by the D0 collaboration, is studied in a next-to-leading order(NLO) global QCD analysis to assess its impact on the proton parton distribution functions(PDFs). We show that these data lead to a significant change in the gluon and charm quark distributions. We demonstrate also that there is an inconsistency between the new high precision HERA I+II combined data and Tevatron measurement. Moreover, in this study we investigate the impact of older EMC measurements of charm structure function F_c~2 on the PDFs and compare the results with those from the analysis of Tevatron data. We show that both of them have the same impact on the PDFs, and thus can be recognized as the same evidence for the inefficiency of perturbative QCD in dealing with charm production in some kinematic regions.     

Lifetime measurements for some n=2 levels in Be-like S ⅩⅢ

Highly ionized Spectra from sulfur obtained at an energy of 80 MeV have been studied in the 19.0～53.0 nm wavelength range. Radiative lifetimes for some n=2 level in Be+-like S ⅩⅢwere measured using he beam-foil time of flight method. The results, using an arbitrarily normalized decay curves analysis, are compared with theoretical predictions and earlier measurement.     

First lattice QCD calculation of semileptonic decays of charmed-strange baryonsΞc

While the standard model is the most successful theory to describe all the interactions and constituents of elementary particle physics,it has been constantly scrutinized for over four decades.Weak decays of charm quarks can be used to measure the coupling strength between quarks in different families and serve as an ideal probe for CP violation.As the lowest charm-strange baryons with three different flavors,Ξ;baryons(composed of csu or csd)have been extensively studied in experiments.In this study,we use state-of-the-art lattice QCD techniques to generate 2+1 clover fermion ensembles with two lattice spacings,a=(0.108,0.080 fm).Then,we present the first ab-initio lattice QCD calculation of the Ξ;→Ξ form factors.Our theoretical results for the Ξc→Ξl;v;decay widths are consistent with and approximately two times more precise than the latest measurements by the ALICE and Belle collaborations.Based on the latest experimental measurements,we independently obtain the quark-mixing matrix element |V;|,which is in good agreement with results from other theoretical approaches.     

Impact of lepton p_T threshold on charge asymmetry predictions for inclusive W boson production in pp collisions at 13 TeV

This paper presents the impact of the lepton transverse momentum p_T~l threshold on the W boson charge asymmetry predictions in perturbative QCD for the inclusive W~++X→l~±v+X production in proton-proton(pp)collisions.The predictions are obtained at various low-p_T~l thresholds p_T~l 20,25,30,and 40 GeV in a fiducial region encompassing both the central and forward detector acceptances in terms of the lepton pseudorapidity0 ≤η_l≤4.5.The predicted distributions for the lepton charge asymmetry,which is defined by η_l(A_(η_l)),at the nextto-next-to-leading order(NNLO) accuracy are compared with the CMS and LHCb data at 8 TeV center-of-mass collision energy.The 8 TeV predictions reproduce the data fairly well within the quoted uncertainties.The predictions from the CT14 parton distribution function(PDF) model are in a slightly better agreement with the data over the other PDF sets that are tested.The 13 TeV predictions using various p_T~l thresholds are reported for A_(η_l) and the charge asymmetries that are defined in terms of the differential cross sections in bins of the W boson rapidity yw(A_(y_w)) and transverse momentum p_T~W(A_(p_T~W)).The NNLO predictions for the A_(η_l),A_(y_w).and A_(p_T~W) distributions are assessed to be in close correlation with the p_T~l value.The A_(η_l) and A_(y_w) distributions are particularly shown to be more correlated at a higher p_T~l threshold.The A_(p_T~W) distributions are also reported from the merged predictions with improved accuracy by the inclusion of the next-to-next-to-next-to-leading logarithm(N'LL) corrections,i.e.,at NNLO+N~3 LL.The predicted distributions from various p_T~l thresholds represent a finer probe in terms of the capability to provide more constraints on the ratio of u and d quark distribution functions in the parton momentum fraction range 10~(-4) x1.     

Search for QCD critical point by transverse velocity dependence of anti-deuteron to deuteron ratio

We propose the transverse velocity(β_T) dependence of the anti-deuteron to deuteron ratio as a new observable to search for the QCD critical point in heavy-ion collisions.The QCD critical point can attract the system evolution trajectory in the QCD phase diagram,which is known as the focusing effect.To quantify this effect,we employ the thermal and hadronic transport model to simulate the dynamical particle emission along a hypothetical focusing trajectory near the critical point.We found that the focusing effect can lead to anomalous β_T dependence on ■/p,■/d and ■/~3 He ratios.We examined the β_T dependence of ■/p and ■/d ratios of central Au+Au collisions at ■=7.7 to 200 GeV measured by the STAR experiment at RHIC.Surprisingly,we only observe a negative slope in β_T dependence of ■/d ratio at ■=19.6 GeV,which indicates the trajectory evolution has passed through the critical region.In the future,we could constrain the location of the critical point and/or width of the critical region by conducting precise measurements on the β_T dependence of the ■/d ratio at different energies and rapidity.     

Constraints on the R-Parity Violating Couplings Using the Newest Measurement of the Decay B_s~0→μ~+μ~-

Recently, the LHCb collaboration reported the first evidence for the decay B0s→μ+μ-. A branching ratio of B(B0s→μ+μ-)=(3.2+1.51.2)×10 9is given. Using the newest data, and together with the most precise predictions of the Standard Model contributions to the decay, we derive the constraints on the combinations of the R-parity violating parameters. Our results are several orders of magnitudes stronger than the constraints in the previous literature. We also update the constraints on the relevant parameters using the upper limit ofB(B0d→μ+μ-).     

Next-to-leading order QCD corrections to the decay of Higgs to vector meson and Z boson

The exclusive decay of the Higgs boson to a vector meson(J/ψ or Υ(1 S)) and Z boson is studied in this work. The decay amplitudes are separated into two parts in a gauge invariant manner. The first part comes from the direct coupling of the Higgs boson to the charm(bottom) quark and the other from the HZZ*or the loop-induced HZγ*vertexes in the standard model. While the branching ratios from the direct channel are much smaller than those of the indirect channel, their interference terms give nontrivial contributions. We further calculate the QCD radiative corrections to both channels, which reduce the total branching ratios by around 20% for both J/ψ and Υ(1S) production. Our results provide a possible chance to check the SM predictions of the Hcc(Hbb)coupling and to seek for hints of new physics at the High Luminosity LHC or future hadron colliders.     

b→cτ■ decay in supersymmetry with R-parity violation

In past years,several hints of lepton flavor universality(LFU)violation have emerged from the b→ct■,and b→sl~+l-data.More recently,the Belle Collaboration has reported the first measurement of the D* longitudinal polarization fraction in the B→D*τV decay.Motivated by this intriguing result,along with the recent measurements of RJ/Ψand τ polarization,we present the study of b→ct■ decays in supersymmetry(SUSY)with R-parity violation(RPV).We consider B→D(*)t■,Bc→ηct■,Bc→J/ψt■ and ∧b→∧ct■ modes and focus on the branching ratios,LFU ratios,forward-backward asymmetries,polarizations of daughter hadrons,and the τ lepton.The RPV SUSY was capable of explaining the RD(*) anomalies at the 2σ level,after taking into account various flavor constraints.In the allowed parameter space,the differential branching fractions and LFU ratios are largely enhanced by the SUSY effects,especially in the large dilepton invariant mass region.Moreover,a lower bound B(B~+→K~+vv)7.37×10~(-6) is obtained.These observables could provide testable signatures at the high-luminosity LHC and SuperKEKB,and correlate with direct searches for SUSY.     

White emission from Tm3+/Tb3+/Eu3+ co-doped fluoride zirconate under ultraviolet excitation

We synthesize Tm3+/Tb3+/Eu3+triply-doped ZrF4–BaF2–LaF3–AlF3–NaF(ZBLAN) transparent glass by using a melt-quenching method. Under excitation of 365 nm, the white emission with Commission internationale deL’Eclairage(CIE) coordinates of(0.33, 0.33) is achieved at the Eu3+concentration of 1.1 mol%. The mechanisms for white emission and the energy transfer process of Tb3+→ Eu3+are discussed in terms of the photoluminescence, photoluminescence excitation spectra, and the light emission decay curves. The nature for the Tb3+→ Eu3+energy transfer is described with the aid of an energy level diagram.     

D^＋→η^（＇）l＋ν_l semileptonic decays in light-cone sum rules

We calculate the D→η transition form factor in light-cone sum rules by taking improved current correlators to avoid the pollution from the twist-3 wave function. We get consistent results of the D+→η(′)l+νl decays with the experimental data. By comparing the difference between the results of the branching ratios of D+→η(′)l+νl from a two-pole parameterization model and from a BZ parameterization model, we find that the two-pole model and the BZ model are comparably believable. One way is supposed for the de...