1,407 research outputs found

    Inclusive hch_c production at BB factories

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    Within the nonrelativistic QCD (NRQCD) factorization framework, we investigate the inclusive production of the hch_c meson associated with either light hadrons or charmed hadrons at BB factory energy s=10.58\sqrt{s}=10.58 GeV. Both the leading color-singlet and color-octet channels are included. For the hch_c production associated with light hadrons, the total production rate is dominated by the color-octet channel, thus the future measurement of this process may impose useful constraint on the value of the color-octet matrix element ; for the hch_c production associated with charmed hadrons, the total production rate is about one order of magnitude smaller, and dominated by the color-singlet channel.Comment: v2, 23 pages, 1 table, 6 figures. Minor corrections, and a note added, accepted for publication in PR

    Short-range force between two Higgs bosons

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    The SS-wave scattering length and the effective range of the Higgs boson in Standard Model are studied using effective-field-theory approach. After incorporating the first-order electroweak correction, the short-range force between two Higgs bosons remains weakly attractive for MH=126M_H=126 GeV. It is interesting to find that the force range is about two order-of-magnitude larger than the Compton wavelength of the Higgs boson, almost comparable with the typical length scale of the strong interaction.Comment: v2, 11 pages, 2 figures, the version accepted for publication in Phys. Lett.

    Reconciling the nonrelativistic QCD prediction and the J/Οˆβ†’3Ξ³J/\psi\to 3\gamma data

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    It has been a long-standing problem that the rare electromagnetic decay process J/Οˆβ†’3Ξ³J/\psi\to 3\gamma is plagued with both large and negative radiative and relativistic corrections. To date it remains futile to make a definite prediction to confront with the branching fraction of J/Οˆβ†’3Ξ³J/\psi\to 3\gamma recently measured by the \textsf{CLEO-c} and \textsf{BESIII} Collaborations. In this work, we investigate the joint perturbative and relativistic correction (i.e. the O(Ξ±sv2){\mathcal O}(\alpha_s v^2) correction, where vv denotes the characteristic velocity of the charm quark inside the J/ψJ/\psi) for this decay process, which turns out to be very significant. After incorporating the contribution from this new ingredient, with the reasonable choice of the input parameters, we are able to account for the measured decay rates in a satisfactory degree.Comment: 7 pages, 1 figure, version accepted for publication in PRD R

    Can NRQCD explain the Ξ³Ξ³βˆ—β†’Ξ·c\gamma\gamma^* \to \eta_c transition form factor data?

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    Unlike the bewildering situation in the Ξ³Ξ³βˆ—β†’Ο€\gamma\gamma^*\to \pi form factor, a widespread view is that perturbative QCD can decently account for the recent \textsc{BaBar} measurement of Ξ³Ξ³βˆ—β†’Ξ·c\gamma\gamma^*\to \eta_c transition form factor. The next-to-next-to-leading order (NNLO) perturbative correction to the Ξ³Ξ³βˆ—β†’Ξ·c,b\gamma\gamma^*\to \eta_{c,b} form factor, is investigated in the NRQCD factorization framework for the first time. As a byproduct, we obtain by far the most precise order-Ξ±s2\alpha_s^2 NRQCD matching coefficient for the Ξ·c,bβ†’Ξ³Ξ³\eta_{c,b}\to \gamma\gamma process. After including the substantial negative order-Ξ±s2\alpha_s^2 correction, the good agreement between NRQCD prediction and the measured Ξ³Ξ³βˆ—β†’Ξ·c\gamma\gamma^*\to \eta_c form factor is completely ruined over a wide range of momentum transfer squared. This eminent discrepancy casts some doubts on the applicability of NRQCD approach to hard exclusive reactions involving charmonium.Comment: 6 pages, 3 figures and 1 table; adding Eqs.(8) and (9) as well as some references, correcting errors in Table 1, updating Fig.3 to include the "light-by-light" contributions, devoting a paragraph to discuss why our strategy of interpreting the NNLO corrections is justified; Accepted by PR

    Next-to-next-to-leading-order QCD corrections to e+eβˆ’β†’J/ψ+Ξ·ce^+e^-\to J/\psi+\eta_c at BB factories

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    Within the nonrelativistic QCD (NRQCD) factorization framework, we compute the long-awaited O(Ξ±s2){\mathcal O}(\alpha_s^2) correction for the exclusive double charmonium production process at BB factories, i.e., e+eβˆ’β†’J/ψ+Ξ·ce^+e^-\to J/\psi+\eta_c at s=10.58\sqrt{s}=10.58 GeV. For the first time, we confirm that NRQCD factorization does hold at next-to-next-to-leading-order (NNLO) for exclusive double charmonium production. It is found that including the NNLO QCD correction greatly reduces the renormalization scale dependence, and also implies the reasonable perturbative convergence behavior for this process. Our state-of-the-art prediction is consistent with the BaBar measurement.Comment: 6 pages, 2 figures, 1 tabl

    Next-to-leading-order QCD corrections to e+eβˆ’β†’H+Ξ³e^+e^-\to H+\gamma

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    The associated production of Higgs boson with a hard photon at lepton collider, i.e., e+eβˆ’β†’HΞ³e^+e^-\to H\gamma, is known to bear a rather small cross section in Standard Model, and can serve as a sensitive probe for the potential new physics signals. Similar to the loop-induced Higgs decay channels Hβ†’Ξ³Ξ³,ZΞ³H\to \gamma\gamma, Z\gamma, the e+eβˆ’β†’HΞ³e^+e^-\to H\gamma process also starts at one-loop order provided that the tiny electron mass is neglected. In this work, we calculate the next-to-leading-order (NLO) QCD corrections to this associated H+Ξ³H+\gamma production process, which mainly stem from the gluonic dressing to the top quark loop. The QCD corrections are found to be rather modest at lower center-of-mass energy range (s<300\sqrt{s}<300 GeV), thus of negligible impact on Higgs factory such as CEPC. Nevertheless, when the energy is boosted to the ILC energy range (sβ‰ˆ400\sqrt{s}\approx 400 GeV), QCD corrections may enhance the leading-order cross section by 20%20\%. In any event, the e+eβˆ’β†’HΞ³e^+e^-\to H\gamma process has a maximal production rate Οƒmaxβ‰ˆ0.08\sigma_{\rm max}\approx 0.08 fb around s=250\sqrt{s}= 250 GeV, thus CEPC turns out to be the best place to look for this rare Higgs production process. In the high energy limit, the effect of NLO QCD corrections become completely negligible, which can be simply attributed to the different asymptotic scaling behaviors of the LO and NLO cross sections, where the former exhibits a milder decrement ∝1/s\propto 1/s , but the latter undergoes a much faster decrease ∝1/s2\propto 1/s^2.Comment: v4, 11 pages, 6 figures, 2 tables; errors in Appendix are fixed; version accepted for publication at PL

    Relativistic Corrections to the Exclusive Decays of C-even Bottomonia into S-wave Charmonium Pairs

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    Within the nonrelativistic quantum chromodynamics (NRQCD) factorization formalism, we compute the relativistic corrections to the exclusive decays of bottomonia with even charge conjugation parity into SS-wave charmonium pairs at leading order in the strong coupling constant. Relativistic corrections are resummed for a class of color-singlet contributions to all orders in the charm-quark velocity vcv_c in the charmonium rest frame. Almost every process that we consider in this work has negative relativistic corrections ranging from -20 to -35,%. Among the various processes, the relativistic corrections of the next-to-leading order in vcv_c to the decay rate for Ο‡b2β†’Ξ·c(mS)+Ξ·c(nS)\chi_{b2}\to \eta_c(mS)+\eta_c(nS) with m,m, n=1n=1 or 2 are very large. In every case, the resummation of the relativistic corrections enhances the rate in comparison with the next-to-leading-order results. We compare our results with available predictions based on the NRQCD factorization formalism. The NRQCD predictions are significantly smaller than those based on the light-cone formalism by an or two orders of magnitudes.Comment: 20 pages, 1 figure. Typos corrected, published versio
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