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Effects of Zb states and bottom meson loops on γ(4S)→γ(1S, 2S)π+π? transitions

Yun-Hua Chen; Martin Cleven; Johanna T. Daub; Feng-Kun Guo; Christoph Hanhart; Bastian Kubis; Ulf-G. Mei遪er; Bing-Song ZouSubjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

We study the dipion transitions (4S) → (nS)π+π? (n = 1, 2). In particular, we consider the effects of the two intermediate bottomoniumlike exotic states Zb(10610) and Zb(10650) as well as bottom meson loops. The strong pion–pion final-state interactions, especially including channel coupling to K ?K in the S-wave, are taken into account modelindependently by using dispersion theory. Based on a nonrelativistic effective field theory we find that the contribution from the bottom meson loops is comparable to those from the chiral contact terms and the Zb-exchange terms. For the (4S) → (2S)π+π? decay, the result shows that including the effects of the Zb-exchange and the bottom meson loops can naturally reproduce the two-hump behavior of the ππ mass spectra. Future angular distribution data are decisive for the identification of different production mechanisms. For the (4S) → (1S)π+π? decay, we show that there is a narrow dip around 1GeV in the ππ invariant mass distribution, caused by the final-state interactions. The distribution is clearly different from that in similar transitions from lower states, and needs to be verified by future data with high statistics. Also we predict the decay width and the dikaon mass distribution of the (4S) → (1S)K+K? process. |

Subjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

If massive neutrinos are Dirac particles, the proposed PTOLEMY experiment will hopefully be able to discover cosmic neutrino background via e+3H ! 3He+e? with a capture rate of ?D 4 yr?1. Recently, it has been pointed out that right-handed com-ponents of Dirac neutrinos could also be copiously produced in the early Universe and become an extra thermal or nonthermal ingredient of cosmic relic neutrinos, enhancing the capture rate to ?D 5:1 yr?1 or ?D 6:1 yr?1. In this work, we investigate the possibility to distinguish between thermal and nonthermal spectra of cosmic relic neu-trinos by measuring the annual modulation of the capture rate. For neutrino masses of 0:1 eV, we have found the amplitude of annual modulation in the standard case is M 0:05%, which will be increased to 0:1% and 0:15% in the presence of additional thermal and nonthermal right-handed neutrinos, respectively. The future detection of such a modulation will be helpful in understanding the Majorana or Dirac nature of massive neutrinos. |

Leptonic Unitarity Triangles and Effective Mass Triangles of the Majorana Neutrinos

Zhi-zhong Xing; Jing-yu ZhuSubjects: Physics >> Nuclear Physics

Given the best-fit results of six neutrino oscillation parameters, we plot the Dirac and Majorana unitarity triangles (UTs) of the 3\times 3 lepton flavor mixing matrix to show their real shapes for the first time. The connections of the Majorana UTs with neutrino-antineutrino oscillations and neutrino decays are explored, and the possibilities of right or isosceles UTs are discussed. In the neutrino mass limit of m_1 \to 0 or m_3 \to 0, which is allowed by current experimental data, we show how the six triangles formed by the effective Majorana neutrino masses \langle m\rangle_{\alpha\beta} (for \alpha, \beta = e, \mu, \tau) and their corresponding component vectors look like in the complex plane. The relations of such triangles to the Majorana phases and to the lepton-number-violating decays H^{++} \to \alpha^+ \beta^+ in the type-II seesaw mechanism are also illustrated. |

The leading twist light-cone distribution amplitudes for the S-wave and P-wave Bc mesons

Ji Xu; Deshan YangSubjects: Physics >> Nuclear Physics

The light-cone distribution amplitudes (LCDAs) serve as important non-perturbative inputs for the study of hard exclusive processes. In this paper, we calculate ten LCDAs at twist-2 for the S-wave and P-wave Bc mesons up to the next-to-leading order (NLO) of the strong coupling alpha_s and leading order of the velocity expansion. Each one of these ten LCDAs is expressed as a product of a perturbatively calculable distribution and a universal NRQCD matrix-element. By use of spin symmetry, only two NRQCD matrix-elements will be involved. The reduction of the number of non-perturbative inputs will improve the predictive power of collinear factorization. |

Subjects: Physics >> Nuclear Physics

Given an accelerator-based neutrino experiment with the beam energy E \lesssim 1 GeV, we expand the probabilities of \nu_\mu \to \nu_e and \overline {\nu}_\mu \to \overline {\nu}_e oscillations in matter in terms of two small quantities \Delta_{21}/\Delta_{31} and A/\Delta_{31}, where \Delta_{21} \equiv m^2_2 - m^2_1 and \Delta_{31} \equiv m^2_3 - m^2_1 are the neutrino mass-squared differences, and A measures the strength of terrestrial matter effects. Our analytical approximations are numerically more accurate than those made by Freund in this energy region, and thus they are particularly applicable for the study of leptonic CP violation in the low-energy MOMENT, ESS\nuSM and T2K oscillation experiments. As a by-product, the new analytical approximations help us to easily understand why the matter-corrected Jarlskog parameter \widetilde{\cal J} peaks at the resonance energy E_* \simeq 0.14 GeV (or 0.12 GeV) for the normal (or inverted) neutrino mass hierarchy, and how the three Dirac unitarity triangles are deformed due to the terrestrial matter contamination. We also affirm that a medium-baseline neutrino oscillation experiment with the beam energy E lying in the E_* \lesssim E \lesssim 2 E_* range is capable of exploring leptonic CP violation with little matter-induced suppression. |

Fast adaptive flat-histogram ensemble to enhance the sampling in large systems

XU Shun; ZHOU Xin; JIANG Yi; WANG YanTingSubjects: Physics >> Interdisciplinary Physics and Related Areas of Science and Technology

An efficient novel algorithm was developed to estimate the Density of States (DOS) for large systems by calculating the ensemble means of an extensive physical variable, such as the potential energy, U, in generalized canonical ensembles to interpolate the interior reverse temperature curve beta S(U) partial derivative S(U)/partial derivative U, where S(U) is the logarithm of the DOS. This curve is computed with different accuracies in different energy regions to capture the dependence of the reverse temperature on U without setting prior grid in the U space. By combining with a U-compression transformation, we decrease the computational complexity from O(N-3/2) in the normal Wang Landau type method to O(N-1/2) in the current algorithm, as the degrees of freedom of system N. The efficiency of the algorithm is demonstrated by applying to Lennard Jones fluids with various N, along with its ability to find different macroscopic states, including metastable states. |

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