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No abstract prepared.
Based on the isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model plus the Skyrme force parameters, the initialization effect is studied in heavy-ion collisions at intermediate energies. We find that there are moderate initialization effects in the following observables: free neutron to proton ratio (n/p), {pi}{sup -}/{pi}{sup +} ratio, and neutron to proton differential flow (F{sub n-p}{sup x}). Effects of initialization are larger for charged {pi}{sup -}/{pi}{sup +} ratios than for n/p ratios. And the effects of initialization are more evident in nuclear reactions at lower incident beam energies. We do not see large effects of initialization for light reaction systems or large asymmetric (neutron-richer) reaction systems. We also see relatively large effects of initialization on the neutron to proton differential flow at relatively lower incident beam energies or with large impact parameters. These results may be useful for the delicate studies of the equation of state of asymmetric nuclear matter.
In the framework of QCD factorization, based on the first order of isospin violation, we study direct CP violation in the decay of B{sub s}{sup 0}{yields}K{sup 0}{rho}{sup 0}({omega}){yields}K{sup 0}{pi}{sup +}{pi}{sup -}, including the effect of {rho}-{omega} mixing. We find that the CP violating asymmetry is large via the {rho}-{omega} mixing mechanism when the invariant mass of the {pi}{sup +}{pi}{sup -} pair is in the vicinity of the {omega} resonance. For the decay of B{sub s}{sup 0}{yields}K{sup 0}{rho}{sup 0}({omega}){yields}K{sup 0}{pi}{sup +}{pi}{sup -}, the maximum CP violating asymmetries can reach about 46%. We also discuss the possibility to observe the predicted CP violating asymmetries at the LHC.
Within the framework of the QCD sum rules, we consider the three-point correlation function, work at the limit q{sup 2}{yields}0 and m{sub {pi}}{yields}0, and pick out the singular term {approx}(1/q{sup 2}) to extract the pionic coupling constants of the 1{sup -+} hybrid meson. Then, we calculate the decay widths of different modes. The decay width of the S-wave modes b{sub 1{pi}}, f{sub 1{pi}} increases quickly as the hybrid meson mass and decay momentum increase. But for the low mass hybrid meson around 1.6 GeV, the P-wave decay mode {rho}{pi} is very important and its width is around 180 MeV, while the widths of {eta}{pi} and {eta}{sup '{pi}} are strongly suppressed. We suggest the experimental search of {pi}{sub 1}(1600) through the decay chains at the Beijing Spectrometer: J/{psi}({psi}{sup '}){yields}{pi}{sub 1}+{gamma} or J/{psi}({psi}{sup '}){yields}{pi}{sub 1}+{rho}, where the {pi}{sub 1} state can be reconstructed through the decay modes {pi}{sub 1}{yields}{rho}{pi}{yields}{pi}{sup +}{pi}{sup -}{pi}{sup 0} or {pi}{sub 1}{yields}f{sub 1}(1285){pi}{sup 0}. It is also interesting to look for {pi}{sub 1} using the available BELLE/BABAR data through the process e{sup +}e{sup -}{yields}{gamma}*{yields}{rho}{pi}{sub 1}, b{sub 1}{pi}{sub 1}, {gamma}{pi}{sub 1}, etc.
We calculate the coupling constants of the decay modes 1{sup -+}{yields}{rho}{pi}, f{sub 1}{pi}, b{sub 1}{pi}, {eta}{pi}, {eta}{sup '}{pi}, a{sub 1}{pi}, f{sub 1}{eta} within the framework of the light-cone QCD sum rule. Then we calculate the partial width of these decay channels, which differ greatly from the existing calculations using phenomenological models. For the isovector 1{sup -+} state, the dominant decay modes are {rho}{pi}, f{sub 1}{pi}. For its isoscalar partner, its dominant decay mode is a{sub 1}{pi}. We also discuss the possible search of the 1{sup -+} state at BESIII, for example through the decay chains J/{psi}({psi}{sup '}){yields}{pi}{sub 1}+{gamma} or J/{psi}({psi}{sup '}){yields}{pi}{sub 1}+{rho}, where {pi}{sub 1} can be reconstructed through the decay modes {pi}{sub 1}{yields}{rho}{pi}{yields}{pi}{sup +}{pi}{sup -}{pi}{sup 0} or {pi}{sub 1}{yields}f{sub 1}(1285){pi}{sup 0}. Hopefully the present work will be helpful to the experimental establishment of the 1{sup -+} hybrid meson.
We present an analysis of exclusive charmless semileptonic B-meson decays based on 377 million B{bar B} pairs recorded with the BABAR detector at the {Upsilon} (4S) resonance. We select four event samples corresponding to the decay modes B{sup 0} {yields} {pi}{sup -}{ell}{sup +}{nu}, B{sup +} {yields} {pi}{sup 0}{ell}{sup +}{nu}, B{sup 0} {yields} {rho}{sup -}{ell}{sup +}{nu}, and B{sup +} {yields} {rho}{sup 0}{ell}{sup +}{nu}, and find the measured branching fractions to be consistent with isospin symmetry. Assuming isospin symmetry, we combine the two B {yields} {pi}{ell}{nu} samples, and similarly the two B {yields} {rho}{ell}{nu} samples, and measure the branching fractions {Beta}(B{sup 0} {yields} {pi}{sup -}{ell}{sup +}{nu}) = (1.41 {+-} 0.05 {+-} 0.07) x 10{sup -4} and {Beta}(B{sup 0} {yields} {rho}{sup 0}{ell}{sup +}{nu}) = (1.75 {+-} 0.15 {+-} 0.27) x 10{sup -4}, where the errors are statistical and systematic. We compare the measured distribution in q{sup 2}, the momentum transfer squared, with predictions for the form factors from QCD calculations and determine the CKM matrix element |V{sub ub}|. Based on the measured partial branching fraction for B {yields} {pi}{ell}{nu} in the range q{sup 2} < 12 GeV{sup 2} and the most recent LCSR calculations we obtain |V{sub ub}| = (3.78 {+-} 0.13{sub -0.40}{sup +0.55}) x 10{sup -3}, where the errors refer to the experimental and theoretical uncertainties. From a simultaneous fit to the data over the full q{sup 2} range and the FNAL/MILC lattice QCD results, we obtain |V{sub ub}| = (2.95 {+-} 0.31) x 10{sup -3} from B {yields} {pi}{ell}{nu}, where the error is the combined experimental and theoretical uncertainty.
No abstract prepared.
We report on a search for CP violation in the decay D{sup {+-}} {yields} K{sub S}{sup 0}{pi}{sup {+-}} using a data set corresponding to an integrated luminosity of 469 fb{sup -1} collected with the BABAR detector at the PEP-II asymmetric energy e{sup +}e{sup -} storage rings. The CP-violating decay rate asymmetry A{sub CP} is determined to be (-0.44 {+-} 0.13(stat) {+-} 0.10(syst))%, consistent with zero at 2.7 {sigma} and with the standard model prediction of (-0.332 {+-} 0.006)%. This is currently the most precise measurement of this parameter.
We consider a scenario (supported by some lattice results) in which a U(1)-breaking condensate survives across the chiral transition in QCD. This scenario has important consequences for the pseudoscalar-meson sector, which can be studied using an effective Lagrangian model. In particular, generalizing the results obtained in two previous papers, where the effects on the radiative decays {eta}, {eta}{sup '{yields}{gamma}{gamma}} were studied, in this paper we study the effects of the U(1) chiral condensate on the strong decays of the ''light'' pseudoscalar mesons, i.e., {eta}, {eta}{sup '}{yields}3{pi}{sup 0}; {eta}, {eta}{sup '}{yields}{pi}{sup +}{pi}{sup -}{pi}{sup 0}; {eta}{sup '}{yields}{eta}{pi}{sup 0}{pi}{sup 0}; {eta}{sup '}{yields}{eta}{pi}{sup +}{pi}{sup -}; and also on the strong decays of an exotic (''heavy'') SU(3)-singlet pseudoscalar state {eta}{sub X}, predicted by the model.
We first present a nonresonant description to charmoniumlike structure Y(4360) in the {psi}(2S){pi}{sup +}{pi}{sup -} invariant mass spectrum of the e{sup +}e{sup -}{yields}{psi}(2S){pi}{sup +}{pi}{sup -} process. The Y(4360) structure is depicted well by the interference effect of the production amplitudes of e{sup +}e{sup -}{yields}{psi}(2S){pi}{sup +}{pi}{sup -} via the intermediate charmonia {psi}(4160)/{psi}(4415) and direct e{sup +}e{sup -} annihilation into {psi}(2S){pi}{sup +}{pi}{sup -}. This fact shows that Y(4360) is not a genuine resonance, which naturally explains why Y(4360) was only reported in its hidden-charm decay channel {psi}(2S){pi}{sup +}{pi}{sup -} and was not observed in the exclusive open-charm decay channel or R-value scan.
We update our analysis of {rho}-{omega} mixing effects in the pion form factor to incorporate the recently published BABAR and KLOE e{sup +}e{sup -}{yields}{pi}{sup +}{pi}{sup -} cross sections. Implications for {tau}-decay-based standard model estimates of the leading order hadronic contribution to the muon anomalous magnetic moment, and for the extraction of the off-diagonal vector meson self-energy matrix element, {Pi}{sub {rho}{omega}}(m{sub {rho}}{sup 2}), are discussed.
The {Lambda}{sub c}(2940){sup +} baryon with quantum numbers J{sup P}=(1/2){sup +} is considered as a hadronic molecule composed of a nucleon and D{sup *} meson. We give predictions for the width of the strong three-body decay processes {Lambda}{sub c}(2940){sup +}{yields}{Lambda}{sub c}(2286){sup +}{pi}{sup +}{pi}{sup -} and {Lambda}{sub c}(2286){sup +}{pi}{sup 0}{pi}{sup 0} in this interpretation. Upcoming experimental facilities like a Super B factory at KEK or LHCb might be able to provide data on these decay modes.
We analyze the decay B{sup 0} {yields} K{sup +} {pi}{sup -} {pi}{sup 0} with a sample of 454 million B{bar B} events collected by the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC, and extract the complex amplitudes of seven interfering resonances over the Dalitz plot. These results are combined with amplitudes measured in B{sup 0} {yields} K{sup 0}{sub s}{pi}{sup +}{pi}{sup -} decays to construct isospin amplitudes from B{sup 0} {yields} K{sup *}{pi} and B{sup 0} {yields} {rho}K decays. We measure the phase of the isospin amplitude {Phi}{sub 3/2}, useful in constraining the CKM unitarity triangle angle {gamma} and evaluate a CP rate asymmetry sum rule sensitive to the presence of new physics operators. We measure direct CP violation in B{sup 0} {yields} K{sup *+}{pi}{sup -} decays at the level of 3 {sigma} when measurements from both B{sup 0} {yields} K{sup +}{pi}{sup -}{pi}{sup 0} and B{sup 0} {yields} K{sup 0}{sub s}{pi}{sup +}{pi}{sup -} decays are combined.
Using a sample of 158 x 10⁶ Υ(2S) events collected with the Belle detector, charmonium and charmoniumlike states with even charge parity are searched for in Υ(2S) radiative decays. No significant Xcl or nc signal is observed, and the following upper limits at 90% confidence level (C. L.) are obtained: Β(Υ(2S)→YXco)<1.0×10 - ⁴, Β(Υ(2S)→yxc1)<3.6×10 - ⁶, Β(Υ(2S)→yxc2)<1.5 x 10 - ⁵, and Β(Υ(2S)→ync)<2.7×10 - ⁵. No significant signal of any charmoniumlike state is observed, and we obtain the limits Β(Υ(2S)→yX(3872)) x Β(X(3872)→π⁺π⁻J/ψ)<0.8×10-6, Β(Υ(2S)→γX(3872))× Β(X(3872)→ π⁺π⁻π⁰Jlψ)<2.4 x 10⁻⁶, Β(Υ(2S)→γX(3915))× Β(X(3915)→ωJ/ψ)<2.8×10⁻⁶, Β(Υ(2S)→γY(4140)) x Β(Y(4140)→$\phi$J/ψ))<1.2 x 10 - ⁶, and Β(Υ(2S)→yX(4350))× Β(X(4350)→$\phi$J/ψ))<1.3×10⁻⁶ at 90% C. L.
Considering the defects of the previous work for estimating the anomalous production rates of e{sup +}e{sup -}{yields}{Upsilon}(1S){pi}{sup +}{pi}{sup -}, {Upsilon}(2S){pi}{sup +}{pi}{sup -} near the peak of the {Upsilon}(5S) resonance at {radical}(s)=10.87 GeV [K. F. Chen et al. (Belle Collaboration), Phys. Rev. Lett. 100, 112001 (2008)], we suggest a new scenario where the contributions from the direct dipion transition and the final-state interactions interfere to result in not only the anomalously large production rates, but also line shapes of the differential widths consistent with experimental measurement when assuming the reactions are due to the dipion emission of {Upsilon}(5S). At the end, we raise a new puzzle that the predicted differential width d{Gamma}({Upsilon}(5S){yields}{Upsilon}(2S){pi}{sup +}{pi}{sup -})/dcos{theta} has a discrepant trend from the data while other predictions are well in accord with the data. It should be further clarified by more accurate measurements carried by future experiments.
Inspired by the newly observed two charged bottomoniumlike states, we consider the possible contribution from the intermediate Z{sub b}(10610) and Z{sub b}(10650) states to the {Upsilon}(5S){yields}{Upsilon}(2S){pi}{sup +}{pi}{sup -} decay process, which naturally explains Belle's previous observation of the anomalous {Upsilon}(2S){pi}{sup +}{pi}{sup -} production near the peak of {Upsilon}(5S) at {radical}(s)=10.87 GeV [K. F. Chen et al. (Belle Collaboration), Phys. Rev. Lett. 100, 112001 (2008)]. The resulting d{Gamma}({Upsilon}(5S){yields}{Upsilon}(2S){pi}{sup +}{pi}{sup -})/dm{sub {pi}}{sup +}{sub {pi}}{sup -} and d{Gamma}({Upsilon}(5S){yields}{Upsilon}(2S){pi}{sup +}{pi}{sup -})/dcos{theta} distributions agree with Belle's measurement after inclusion of these Z{sub b} states. This formalism also reproduces the Belle observation of the double-peak structure and its reflection in the {Upsilon}(2S){pi}{sup +} invariant mass spectrum of the {Upsilon}(5S){yields}{Upsilon}(2S){pi}{sup +}{pi}{sup -} decay.