1,296 research outputs found

    Factorization of Radiative Leptonic Decays of Bβˆ’B^- and Dβˆ’D^- Mesons Including the Soft Photon Region

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    In this work, we study the radiative leptonic decays of Bβˆ’B^- and Dβˆ’D^- mesons using factorization approach. Factorization is proved to be valid explicitly at 1-loop level at any order of O(Ξ›QCD/mQ)O(\Lambda_{\rm QCD}\left/m_Q\right.). We consider the contribution in the soft photon region that EΞ³βˆΌΞ›QCD2/mQE_{\gamma} \sim \left. \Lambda^2_{\rm QCD} /\right. m_Q. The numerical results shows that, the soft photon region is very important for both the BB and DD mesons. The branching ratios of Bβ†’Ξ³eΞ½eB\to \gamma e\nu_e is 5.21Γ—10βˆ’65.21\times 10^{-6}, which is about 33 times of the result obtained by only considering the hard photon region Eγ∼mQE_{\gamma}\sim m_Q. And for the case of Dβ†’Ξ³eΞ½eD\to \gamma e\nu_e, the result of the branching ratio is 1.92Γ—10βˆ’51.92\times 10^{-5}.Comment: arXiv admin note: text overlap with arXiv:1409.035

    Factorization of Radiative Leptonic Decays of Bβˆ’B^- and Dβˆ’D^- Mesons

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    In this work, we study the factorization of the radiative leptonic decays of Bβˆ’B^- and Dβˆ’D^- mesons, the contributions of the order O(Ξ›QCD/mQ)O(\Lambda _{\rm QCD}\left/m_Q\right.) are taken into account. The factorization is proved to be valid explicitly at the order O(Ξ±sΞ›QCD/mQ)O(\alpha _s\Lambda _{\rm QCD}\left/m_Q\right.). The hard kernel is obtained. The numerical results are calculated using the wave-function obtained in relativistic potential model. The O(Ξ›QCD/mQ)O(\Lambda _{\rm QCD}\left/m_Q\right.) contribution is found to be very important, the correction to the decay amplitudes of Bβˆ’β†’Ξ³eΞ½Λ‰B^-\to \gamma e\bar{\nu} is about 20%βˆ’30%20\% - 30\%. For DD mesons, the O(Ξ›QCD/mQ)O(\Lambda _{\rm QCD}\left/m_Q\right.) contributions are more important.Comment: 26 pages, 8 figures. Version to appear in Nucl. Phys.

    Constraints on anomalous quartic gauge couplings via WΞ³jjW\gamma jj production at the LHC

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    The vector boson scattering at the Large Hadron Collider (LHC) is sensitive to anomalous quartic gauge couplings (aQGCs). In this paper, we investigate the aQGC contribution to Wγjj W \gamma jj production at the LHC with s=13\sqrt{s}=13 TeV in the context of an effective field theory (EFT). The unitarity bound is applied as a cut on the energy scale of this production process, which is found to have significant suppressive effects on the signals. To enhance the statistical significance, we analyse the kinematic and polarization features of the aQGC signals in detail. We find that the polarization effects induced by the aQGCs are unique and can discriminate the signals from the SM backgrounds well. With the proposed event selection strategy, we obtain the constraints on the coefficients of dimension-8 operators with current luminosity. The results indicate that the process pp→Wγjjpp \to W \gamma jj is powerful for searching for the OM2,3,4,5O_{M_{2,3,4,5}} and OT5,6,7O_{T_{5,6,7}} operators.Comment: 29 pages, 11 figures, 7 tables, to be published in Chinese Physics

    A Large-field J=1-0 Survey of CO and Its Isotopologues Toward the Cassiopeia A Supernova Remnant

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    We have conducted a large-field simultaneous survey of 12^{12}CO, 13^{13}CO, and C18^{18}O J=1βˆ’0J=1-0 emission toward the Cassiopeia A (Cas A) supernova remnant (SNR), which covers a sky area of 3.5βˆ˜Γ—3.1∘3.5^{\circ}\times3.1^{\circ}. The Cas giant molecular cloud (GMC) mainly consists of three individual clouds with masses on the order of 104βˆ’105Β MβŠ™10^4-10^5\ M_{\odot}. The total mass derived from the 13CO\rm{^{13}CO} emission of the GMC is 2.1Γ—105Β MβŠ™\times10^{5}\ M_{\odot} and is 9.5Γ—105Β MβŠ™\times10^5\ M_{\odot} from the 12CO\rm{^{12}CO} emission. Two regions with broadened (6βˆ’-7 km sβˆ’1^{-1}) or asymmetric 12^{12}CO line profiles are found in the vicinity (within a 10β€²Γ—10β€²'\times10' region) of the Cas A SNR, indicating possible interactions between the SNR and the GMC. Using the GAUSSCLUMPS algorithm, 547 13^{13}CO clumps are identified in the GMC, 54%\% of which are supercritical (i.e. Ξ±vir<2\alpha_{\rm{vir}}<2). The mass spectrum of the molecular clumps follows a power-law distribution with an exponent of βˆ’2.20-2.20. The pixel-by-pixel column density of the GMC can be fitted with a log-normal probability distribution function (N-PDF). The median column density of molecular hydrogen in the GMC is 1.6Γ—10211.6\times10^{21} cmβˆ’2^{-2} and half the mass of the GMC is contained in regions with H2_2 column density lower than 3Γ—10213\times10^{21} cmβˆ’2^{-2}, which is well below the threshold of star formation. The distribution of the YSO candidates in the region shows no agglomeration.Comment: 24 pages, 18 figure

    Radiative Leptonic Decays of the charged BB and DD Mesons Including Long-Distance Contribution

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    In this work we study the radiative leptonic decays of Bβˆ’B^-, Dβˆ’D^- and Dsβˆ’β†’Ξ³lΞ½Λ‰D_s^-\to \gamma l \bar{\nu}, including both the short-distance and long-distance contributions. The short-distance contribution is calculated by using the relativistic quark model, where the bound state wave function we used is that obtained in the relativistic potential model. The long-distance contribution is estimated by using vector meson dominance model.Comment: 8 pages, 4 figures, 3 table

    Standard Model of Particle Physics Violating Crypto-Nonlocal Realism

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    It has been well established that quantum mechanics (QM) violates Bell inequalities (BI), which are consequences of local realism (LR). Remarkably QM also violates Leggett inequalities (LI), which are consequences of a class of nonlocal realism called crypto-nonlocal realism (CNR). Both LR and CNR assume that measurement outcomes are determined by preexisting objective properties, as well as hidden variables (HV) not considered in QM. We extend CNR and LI to include the case that the measurement settings are not externally fixed, but determined by hidden variables (HV). We derive a new version of LI, which is then shown to be violated by entangled BdB_d mesons, if charge-conjugation-parity (CP) symmetry is indirectly violated, as indeed established. The experimental result is quantitatively estimated by using the indirect CP violation parameter, and the maximum of a suitably defined relative violation is about 2.7%2.7\%. Our work implies that standard model (SM) of particle physics violates CNR. Our LI can also be tested in other systems such as photon polarizations.Comment: 28 page
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