The Experts below are selected from a list of 21984 Experts worldwide ranked by ideXlab platform
Kuangta Chao - One of the best experts on this subject based on the ideXlab platform.
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qcd radiative correction to color Octet j ψ inclusive production at b factories
Physical Review D, 2010Co-Authors: Yujie Zhang, Kai Wang, Kuangta ChaoAbstract:In nonrelativistic quantum chromodynamics (NRQCD), we study the next-to-leading order (NLO) QCD radiative correction to the color-Octet J/{psi} inclusive production at B factories. Compared with the leading-order (LO) result, the NLO QCD corrections are found to enhance the short-distance coefficients in the color-Octet J/{psi} production e{sup +}e{sup -{yields}}cc({sup 1}S{sub 0}{sup (8)} or {sup 3}P{sub J}{sup (8)})g (with J=0, 1, 2) by a factor of about 1.9. Moreover, the peak at the end point in the J/{psi} energy distribution predicted at LO can be smeared by the NLO corrections, but the major color-Octet contribution still comes from the large energy region of J/{psi}. By fitting the latest data of {sigma}(e{sup +}e{sup -{yields}}J/{psi}+X{sub non-cc}) observed by Belle, we find that the values of color-Octet matrix elements are much smaller than expected earlier by using the naive velocity scaling rules or extracted from fitting experimental data with LO calculations. As the most stringent constraint by setting the color-singlet contribution to be zero in e{sup +}e{sup -{yields}}J/{psi}+X{sub non-cc}, we get an upper limit of the color-Octet matrix element, +4.0 /m{sub c}{sup 2}<(2.0{+-}0.6)x10{sup -2} GeV{sup 3} at NLO in {alpha}{sub s}.
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Upsilon decay to two-charm quark jets as a Probe of the Color Octet Mechanism
Physical Review D, 2008Co-Authors: Yujie Zhang, Kuangta ChaoAbstract:We calculate the decay rate of bottomonium to two charm-quark jets {upsilon}{yields}cc at the tree level and one-loop level including color-singlet and color-Octet bb annihilations. We find that the short-distance coefficient of the color-Octet piece is much larger than the color-singlet piece, and that the QCD correction will change the end point behavior of the charm quark jet. The color-singlet piece is strongly affected by the one-loop QCD correction. In contrast, the QCD correction to the color-Octet piece is weak. Once the experiment can measure the branching ratio and energy distribution of the two charm-quark jets in the {upsilon} decay, the result can be used to test the color-Octet mechanism or give a strong constraint on the color-Octet matrix elements.
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$\Upsilon$ radiative decays to light quark jets and color Octet mechanism
Communications in Theoretical Physics, 2006Co-Authors: Y. Gao, Yujie Zhang, Kuangta ChaoAbstract:We study radiative decays of $\Upsilon$ to light quark jets in nonrelativistic QCD by taking both the color singlet and color Octet $b\bar b$ operators into consideration. The cut for quark jet energy and cut for the angle between two quark jets are introduced. The sensitivity to the soft and collinear singularities in the loop integrals are greatly reduced by these cuts. With the jet energy cut of about 1 GeV, and the jet angle cut of about $36^\circ$, the branching ratio for $\Upsilon\to\gamma q\bar q$ is found to be $8.2\times 10^{-4}$ from color singlet contributions. The color Octet contributions could be much larger than that of color singlet, depending on the estimate of the color Octet matrix elements. This process may provide a new test for the color Octet mechanism in nonrelativistic QCD.
Mark B. Wise - One of the best experts on this subject based on the ideXlab platform.
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Color Octet scalar production at the CERN LHC
Physical Review D, 2007Co-Authors: Moira I. Gresham, Mark B. WiseAbstract:New physics at the weak scale that can couple to quarks typically gives rise to unacceptably large flavor changing neutral currents. An attractive way to avoid this problem is to impose the principle of minimal flavor violation. Recently it was noted that in minimal flavor violation only scalars with the same gauge quantum numbers as the standard model Higgs doublet or color Octet scalars with the same weak quantum numbers as the Higgs doublet can couple to quarks. In this paper we compute the one-loop rate for production of a single color Octet scalar through gluon fusion at the LHC, which can become greater than the tree level pair production rate for Octet scalar masses around a TeV. We also calculate the precision electroweak constraint from Z-->[overline b]b; this constraint on color Octet mass and Yukawa coupling affects the allowed range for single Octet scalar production through gluon fusion.
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The Octet structure function and radiative quarkonia decays
Physics Letters B, 1997Co-Authors: I. Z. Rothstein, Mark B. WiseAbstract:The operator product expansion, in conjunction with the power counting of non-relativistic field theory, is used to examine the end-point region of the radiative decay of heavy quark bound states with 3S1 quantum numbers, QQ → γ + X. We identify an infinite class of operators that determine the shape of the photonic end-point spectrum. These operators can be resummed to form an Octet structure function which parameterizes the energy of the dynamical gluon content of the leading Octet Fock state component of the quarkonium. This color-Octet contribution is important when the photon spectrum is examined with a resolution given by ΔEγ ∼ mQν2, where ν is the magnitude of the relative quark velocity. The formalism used makes explicit the shift of the end-point from its partonic to its hadronic value.
Yujie Zhang - One of the best experts on this subject based on the ideXlab platform.
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qcd radiative correction to color Octet j ψ inclusive production at b factories
Physical Review D, 2010Co-Authors: Yujie Zhang, Kai Wang, Kuangta ChaoAbstract:In nonrelativistic quantum chromodynamics (NRQCD), we study the next-to-leading order (NLO) QCD radiative correction to the color-Octet J/{psi} inclusive production at B factories. Compared with the leading-order (LO) result, the NLO QCD corrections are found to enhance the short-distance coefficients in the color-Octet J/{psi} production e{sup +}e{sup -{yields}}cc({sup 1}S{sub 0}{sup (8)} or {sup 3}P{sub J}{sup (8)})g (with J=0, 1, 2) by a factor of about 1.9. Moreover, the peak at the end point in the J/{psi} energy distribution predicted at LO can be smeared by the NLO corrections, but the major color-Octet contribution still comes from the large energy region of J/{psi}. By fitting the latest data of {sigma}(e{sup +}e{sup -{yields}}J/{psi}+X{sub non-cc}) observed by Belle, we find that the values of color-Octet matrix elements are much smaller than expected earlier by using the naive velocity scaling rules or extracted from fitting experimental data with LO calculations. As the most stringent constraint by setting the color-singlet contribution to be zero in e{sup +}e{sup -{yields}}J/{psi}+X{sub non-cc}, we get an upper limit of the color-Octet matrix element, +4.0 /m{sub c}{sup 2}<(2.0{+-}0.6)x10{sup -2} GeV{sup 3} at NLO in {alpha}{sub s}.
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Upsilon decay to two-charm quark jets as a Probe of the Color Octet Mechanism
Physical Review D, 2008Co-Authors: Yujie Zhang, Kuangta ChaoAbstract:We calculate the decay rate of bottomonium to two charm-quark jets {upsilon}{yields}cc at the tree level and one-loop level including color-singlet and color-Octet bb annihilations. We find that the short-distance coefficient of the color-Octet piece is much larger than the color-singlet piece, and that the QCD correction will change the end point behavior of the charm quark jet. The color-singlet piece is strongly affected by the one-loop QCD correction. In contrast, the QCD correction to the color-Octet piece is weak. Once the experiment can measure the branching ratio and energy distribution of the two charm-quark jets in the {upsilon} decay, the result can be used to test the color-Octet mechanism or give a strong constraint on the color-Octet matrix elements.
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$\Upsilon$ radiative decays to light quark jets and color Octet mechanism
Communications in Theoretical Physics, 2006Co-Authors: Y. Gao, Yujie Zhang, Kuangta ChaoAbstract:We study radiative decays of $\Upsilon$ to light quark jets in nonrelativistic QCD by taking both the color singlet and color Octet $b\bar b$ operators into consideration. The cut for quark jet energy and cut for the angle between two quark jets are introduced. The sensitivity to the soft and collinear singularities in the loop integrals are greatly reduced by these cuts. With the jet energy cut of about 1 GeV, and the jet angle cut of about $36^\circ$, the branching ratio for $\Upsilon\to\gamma q\bar q$ is found to be $8.2\times 10^{-4}$ from color singlet contributions. The color Octet contributions could be much larger than that of color singlet, depending on the estimate of the color Octet matrix elements. This process may provide a new test for the color Octet mechanism in nonrelativistic QCD.
Mustafa Savci - One of the best experts on this subject based on the ideXlab platform.
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Octet negative parity to Octet positive parity electromagnetic transitions in light cone QCD
Journal of Physics G: Nuclear and Particle Physics, 2014Co-Authors: Takhmasib Aliev, Mustafa SavciAbstract:Light cone QCD sum rules for the electromagnetic transition form factors among positive and negative parity Octet baryons are derived. The unwanted contributions of the diagonal transitions among positive parity Octet baryons are eliminated by combining the sum rules derived from different Lorentz structures. The Q2 dependence for the transversal and longitudinal helicity amplitudes are studied.
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Octet baryon magnetic moments in light cone QCD sum rules
Physical Review D, 2002Co-Authors: Tahmasib Aliev, Altuğ Ozpineci, Mustafa SavciAbstract:Octet baryon magnetic moments are calculated in framework of the light cone QCD sum rules. The analysis is carried for the general form of the interpolating currents for Octet baryons. A comparison of our results on the magnetic moments of Octet baryons with the predictions of other approaches and experimental data is presented.
Andrea Petrelli - One of the best experts on this subject based on the ideXlab platform.
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Color-Octet effects in radiative Υ decays
Physical Review D, 1999Co-Authors: Fabio Maltoni, Andrea PetrelliAbstract:We investigate the effects of color-Octet contributions to the radiative \ensuremath{\Upsilon} decay within the Bodwin, Braaten, and Lepage nonrelativistic QCD (NRQCD) framework. We compute the short-distance coefficients at next-to-leading order (NLO) in ${\ensuremath{\alpha}}_{s}$ for the most relevant color-Octet intermediate states and consider photons coming both from the coupling to hard processes (``direct'') and by collinear emission from light quarks (``fragmentation''). An estimate for the nonperturbative matrix elements which enter in the final result is then obtained. By comparing the NRQCD prediction at NLO for total decay rates with the experimental data, it is found that the nonperturbative parameters must be smaller than expected from the naive scaling rules of NRQCD. Nevertheless, color-Octet contributions to the shape of the photon spectrum turn out to be significant.