Searching for a_(0)(980)-meson parton distribution function

In this paper,we calculate the scalar a_(0)(980)-meson leading-twist wave function by using the light-cone harmonic oscillator model(LCHO),where the model parameters are determined by fitting theξ-moments■of its light-cone distribution amplitudes.Then,the a_(0)(980)-meson leading-twist light-cone distribution amplitudes with three different scalesζ=(1.0,2.0,5.2)Ge V are given.After constructing the relationship between the a_(0)(980)-meson leading-twist parton distribution functions/valence quark distribution function and its LCHO wave function,we exhibit the■(x,ζ)and■(x,ζ)with different scales.Furthermore,we also calculate the Mellin moments of the a_(0)(980)-meson’s valence quark distribution function■with n=(1,2,3),i.e.■=0.027,■=0.018 and■=0.013.Finally,the scale evolution for the ratio of the Mellin moments x■are presented.

Investigation of Z-boson decay into Ξ_(bc) and Ξ_(bb) baryons within the NRQCD factorization approach

Z-boson decay provides a good opportunity to search for theΞbQ baryon because a large number of its events can be collected at high energy colliders.In this paper,we perform a complete investigation of the indirect production of theΞbc andΞbb baryons via the Z-boson decay process Z→Ξbo+b+Q with a Q=(c,b)quark under the NRQCD factorization approach.After considering the contibution from the diquark states(be)PSil3/6,<bc)[^(1)Sol3/6,(bb)[^(3)Sol6,and(bb)[3S1l3,the calculated branching fractions are B(Z-→Ξbe+X)=3.595×10^(-5)and B(Z→Ξbb+X)=1.213×10^(-6).Furthermore,theΞbe andΞbb production events are predicted to be of the order of 104 and 103 at the LHC collider,and the order of 107 and 106 for the CEPC collider.We then estimate the produc tion ratio for Z→c2(bb)→Ξbc+X withΞbc→Λ^(+)_(c)in Z-boson decay,that is,R(Z→cc→Ξ0bc+X)~0(10^(-6))br and R(Z→bb→Ξbc+X)~0(10^(-5)),respectively.Finally,we present the differential decay widths ofΞbc andΞbb with respect to 823 and z distributions and analyze the uncertainties.

B_(c)→J/ψhelicity form factors and the B_(c)^(+)→J/ψ+(P,V,ℓ^(+)ν_(ℓ))decays

In this paper,we calculate the B_(c)→J/ψhelicity form factors(HFFs)up to twist-4 accuracy by using the light-cone sum rules(LCSR)approach.After extrapolating those HFFs to the physically allowable q^(2)region,we investigate the B_(c)^(+)-meson two-body decays and semi-leptonic decays B_(c)^(+)→J/ψ+(P,V,ℓ^(+)ν_(ℓ)),where P/V stand for light pseudoscalar and vector mesons,respectively.The branching fractions can be derived using the CKM matrix element and the B_(c)lifetime from the Particle Data Group,and we obtain B(B^(+)_(c)→J/ψπ^(+))=(0.136+0.002−0.002)%,B(B^(+)_(c)→J/ψK^(+))=(0.010+0.000−0.000)%,B(B^(+)_(c)→J/ψρ+)=(0.768+0.029−0.033)%,B(B^(+)_(c)→J/ψK^(∗+))=(0.043+0.001−0.001)%,B(B^(+)_(c)→J/ψ_(μ)+ν_(μ))=(2.802+0.526−0.675)%and B(B^(+)_(c)→J/ψτ^(+)ν_(τ))=(0.559+0.131−0.170)%.We then obtain R_(π^(+)/μ+ν_(μ))=0.048+0.009−0.012 and R_(K^(+)/π^(+))=0.075+0.005−0.005,which agree with the LHCb measured value within 1σ-error.We also obtain R_(J/ψ)=0.199+0.060−0.077,which like other theoretical predictions,is consistent with the LHCb measured value within 2σ-error.These imply that the HFFs under the LCSR approach are also applicable to the B+c meson two-body decays and semi-leptonic decays B+c→J/ψ+(P,V,ℓ^(+)ν_(ℓ)),and the HFFs obtained using LCSR in a new way implies that there may be new physics in the B_(c)→J/ψℓ^(+)ν_(ℓ)semi-leptonic decays.

D→P(π,K)helicity form factors within light-cone sum rule approach

In this study,D→P(π,K) helicity form factors(HFFs) are investigated by applying the QCD light-cone sum rule(LCSR) approach.The calculation accuracy is up to the next-to-leading order(NLO) gluon radiation correction of twist-(2,3) distribution amplitude.The resultant HFFs at a large recoil point are Pt,0π(0)=0.688-0.024+0.020 and Pt,0K(O)=0.780-0.029+0.024,in which the contributions from the three particles of the leading order(LO) are so small that they can be safely neglected.The maximal contribution of the NLO gluon radiation correction for Pt,0r,K(0) is less than3%.After extrapolating the LCSR predictions for these HFFs to the whole q2-region,we obtain the decay widths for semileptonic decay processes D→Plvl,which are consistent with the BES-Ⅲ collaboration predictions within error limits.After considering the D+/D0-meson lifetime,we give the branching fractions of D→Plvl with l=e,μ;our predictions also agree with the BES-Ⅲ collaboration results within error limits,especially for the D→πlvl decay process.Finally,we present the forward-backward asymmetry AFBl(q2) and lepton convexity parameter CFl(q2),and further calculate the mean value of these two observations,<AFBl> and {CFl),which may provide a way to test those HFFs in future experiments.

The B→πlv_l semileptonic decay within the LCSR approach under heavy quark effective field theory

The heavy quark effective field theory(HQEFT)provides an effective way to deal with heavy meson decays.In this paper,we adopt two different correlators to derive the light-cone sum rules(LCSR)for the B→πtransition form factors(TFFs)in the framework of HQEFT.We label the two LCSR results as LCSR-u and LCSR-R,which stand for the conventional correlator and the right-handed correlator.We observe that the correlation parameter|ρRU|for the branching ratio B(B→πlv_l)is^0.85,implying a consistency of LCSRs with the other correlators.Furthermore,we obtain|V_(ub)|_(LCSR-u)=(3.45_(-0.20)^(+0.28)±0.13_(exp))×10^(-3)and|V_(ub)|_(LCSR-R)=(3.38_(-0.16)^(+0.22)±0.12_(exp))×10^(-3).We also obtain R_π|_(LCSR-u)=0.68_(-0.09)^(+0.10)and R_π|_(LCSR-R)=0.65_(-0.11)^(+0.13),both of which agree with the lattice QCD predictions.Thus,HQEFT provides a useful framework for studying B meson decays.Moreover,by using the right-handed correlator,the twist-2 terms are dominant in TFF f^+(q^2),as their contribution is over^97%in the whole q^2 region,while the large twist-3 uncertainty of the conventional correlator is greatly suppressed.Hence,the LCSR-R predictions can be used to test the properties of the various models for the pion twist-2 distribution amplitudes.