119071655
The $J/\psi$ production associated with a hard photon and the color octet signature in $e^{+} e^{-}$ annihilation
$J/\ensuremath{\psi}$ production associated with a hard photon in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation, being of a QED nature, is investigated thoroughly in this paper. To show its influence on the observation of the color-octet signature in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation via $J/\ensuremath{\psi}$ inclusive production, the cross sections of $J/\ensuremath{\psi}$ production through different mechanisms at various energies are compared quantitatively by presenting them in figures together. The contribution from the production associated with a hard photon to the inclusive production of $J/\ensuremath{\psi}$ is pointed out to be significant at the concerned energies; thus, the influence of it on the observation of the color-octet signature should be dealt with carefully.
126140919
Automatic reduction of loop amplitudes
33938812
Projection scheme for handling large-number cancellation related to gauge invariance.
A scheme, the so-called {open_quote}{open_quote}projection,{close_quote}{close_quote} for handling singularities in processes such as {ital e}{sup +}{ital e}{sup {minus}}{r_arrow}{ital t{bar b}e{sup {minus}}}{bar {nu}} (or {ital e}{sup +}{ital e}{sup {minus}}{r_arrow}{ital u{bar d}e{sup {minus}}}{bar {nu}}) is proposed. In the scheme, with the help of gauge invariance, the large power quantities ({ital s}/{ital m}{sup 2}{sub {ital e}}){sup {ital n}} ({ital n}{ge}1;{ital s}{r_arrow}{infinity}) are removed from the calculation totally, while in the usual schemes the large quantities appear and only will be canceled at last. The advantages of the scheme in numerical calculations are obvious; thus, we focus our discussions mainly on the advantages of the scheme in the special case where the absorptive part for some propagators relevant to the process could not be ignored, and a not satisfactory but widely adopted approximation is made; i.e., a finite constant {open_quote}{open_quote}width{close_quote}{close_quote} is introduced to approximate the absorptive part of the propagators phenomenologically even though QED gauge invariance is violated. {copyright} {ital 1996 The American Physical Society.}
118632086
J/psi polarization in photoproduction up to the next-to-leading order of QCD
We investigate the J/psi polarization in photoproduction at the Hadron Electron Ring Accelerator (HERA) up to the next-to-leading order of QCD. The results show that the transverse momentum p(t) and energy fraction z distributions of J/psi production do not agree with the observed ones very well. The theoretical uncertainties for the z distributions of the J/psi polarization parameters with respect to various choices of the renormalization and factorization scales are too large to give a definite predication. The uncertainties for the p(t) distributions of these parameters are small when p(t) > 3 GeV and the obtained p(t) distributions cannot describe the experimental data even in this region.
118808651
Inclusive J/\psi Production In \Upsilon Decay Via Color-singlet Mechanism
In this work, we have calculated the tree level color-singlet contribution to the inclusive $J/\ensuremath{\psi}$ production in $\ensuremath{\Upsilon}$ decay of the ${\ensuremath{\alpha}}_{s}^{5}$ order QCD process $\ensuremath{\Upsilon}\ensuremath{\rightarrow}J/\ensuremath{\psi}+c\overline{c}g$ and ${\ensuremath{\alpha}}^{2}{\ensuremath{\alpha}}_{s}^{2}$ order QED processes $\ensuremath{\Upsilon}\ensuremath{\rightarrow}{\ensuremath{\gamma}}^{*}\ensuremath{\rightarrow}J/\ensuremath{\psi}+c\overline{c}$ and $\ensuremath{\Upsilon}\ensuremath{\rightarrow}J/\ensuremath{\psi}+gg$. It is found that the contribution of the QED processes is comparable with that of the QCD process and the numerical results of the QCD process alone are about an order of magnitude smaller than the previous theoretical predictions. Our prediction in total is $4.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ which is about an order of magnitude smaller than the recent CLEO measurement on the branching fraction $\mathcal{B}(\ensuremath{\Upsilon}\ensuremath{\rightarrow}J/\ensuremath{\psi}+X)$. It indicates that the $J/\ensuremath{\psi}$ production mechanism in $\ensuremath{\Upsilon}$ decay is not well understood and further theoretical work and experimental analysis are still necessary.
118291411
Next-to-Leading-Order QCD corrections to $J/\psi (\upsilon) + \gamma$ production at the LHC
In this work, we calculate the next-to-leading-order (NLO) QCD corrections to the process $p+p \to J/\psi + \gamma$ via the color-singlet mechanism at the LHC. The results show that the partial cross section ($p_t^{J/\psi}>$3GeV and $|y^{J/\psi,\gamma}|<$3) is enhanced by a factor of about 2.0, and the differential cross section can be enhanced by two orders of magnitude in the large transverse momentum region of $J/\psi$. Furthermore, the polarization of $J/\psi$ changes from transverse polarization at leading-order to longitudinal polarization at NLO. For the inclusive $J/\psi$ hadroproduction, it is known that the color-octet contributions are one order of magnitude larger than the color-singlet contribution, and the polarization distribution is dominated by the color-octet behavior at NLO. In contrast, for $J/\psi+\gamma$ production the color-singlet contribution is of the same order as the color-octet contribution, and the polarization distribution arises from both the color-singlet and color-octet. Therefore, measurements of $J/\psi$ production associated with a direct photon at the hadron collider could be an important supplement to testify the theoretical framework treating with the heavy quarkonium. In addition, an NLO QCD correction to $\Upsilon+\gamma$ production at the LHC is also presented in this paper.
118674100
J/ψ production via photon fragmentation at hadron colliders
The transverse momentum (p(t)) distributions of production and polarization for J/psi measured by CDF Collaboration are still challenging our understanding of the heavy quarkonium production mechanism even with recent significant theoretical progresses on the next-to-leading-order (NLO) QCD calculation. We investigate an interesting mechanism for J/psi production at hadron collider, pp((p) over bar) -> gamma* (J/psi) + X with J/psi from a virtual photon gamma* fragmentation. Our calculations show that the J/psi p(t) distribution in the photon fragmentation process up to NLO in alpha(s) will be larger than that of the conventional J/psi production from the color-singlet mechanism at NLO when p(t) > 26 (35) GeV at the Tevatron (LHC) and reach about 6 (10) times of the conventional one when p(t) = 50 (100) GeV at the Tevatron (LHC), in spite of a suppression factor (alpha/alpha(s))(2) that is associated with the QED and QCD coupling constants. In addition, it also has large impact on the p(t) distribution of J/psi polarization in large p(t) region. Therefore, it is an important mechanism for J/psi production at large p(t) region especially for the LHC. (c) 2012 Elsevier B.V. All rights reserved.
32357992
Charmonium Decays of Y(4260), psi(4160), and psi(4040).
Using data collected with the CLEO detector operating at the CESR e+e- collider at sqrt[s]=3.97-4.26 GeV, we investigate 15 charmonium decay modes of the psi(4040), psi(4160), and Y(4260) resonances. We confirm, at 11 sigma significance, the BABAR Y(4260)-->pi+pi- J/psi discovery, make the first observation of Y(4260)--> pi(0)pi(0) J/psi (5.1 sigma), and find the first evidence for Y(4260)-->K+K- J/psi(3.7 sigma). We measure e+e- cross sections at sqrt[s]=4.26 GeV as sigma(pi+pi- J/psi)=58(+12)(-10)+/-4 pb, sigma(pi(0)pi(0) J/psi)=23(+12)(-8)+/-1 pb, and sigma(K+K- J/psi)=9(+9)(-5)+/-1 pb, in which the uncertainties are statistical and systematic, respectively. Upper limits are placed on other decay rates from all three resonances.
7637272
Improved measurement of B(D+ --> mu+nu) and the pseudoscalar decay constant fD+.
We extract a relatively precise value for the decay constant of the meson by measuring B(D+ --> mu+nu) = (4.40 +/-0.66(+0.09)(-0.12) x 10(-4) using 281 pb(-1) of data taken on phi(3770) the resonance with the CLEO-c detector. We find fD+ = (222.6 +/- 16.7(+2.8)(-3.4)) MeV, and compare with current theoretical calculations. We also set a 90% confidence upper limit on B(D+e+nu)< 2.4 x 10(-5) which constrains new physics models.
16565778
Electrical properties of carbon fiber support systems
Abstract Carbon fiber support structures have become common elements of detector designs for high energy physics experiments. Carbon fiber has many mechanical advantages but it is also characterized by high conductivity, particularly at high frequency, with associated design issues. This paper discusses the elements required for sound electrical performance of silicon detectors employing carbon fiber support elements. Tests on carbon fiber structures are presented indicating that carbon fiber must be regarded as a conductor for the frequency region of 10–100 MHz. The general principles of grounding configurations involving carbon fiber structures will be discussed. To illustrate the design requirements, measurements performed with a silicon detector on a carbon fiber support structure at small radius are presented. A grounding scheme employing copper–kapton mesh circuits is described and shown to provide adequate and robust detector performance.
118444783
The QED contribution to $J/\psi$ plus light hadrons production at B-factories
To understand the direct $J/\psi+X_{\mathrm{non-c\bar{c}}}$ production mechanism in $e^{+}e^{-}$ annihilation, in this work, we propose to measure the inclusive $J/\psi$ plus light hadrons (LH) production at B-factories and present a detailed study on its QED production due to $\psi(2S)$ feed-down, where the $\psi(2S)$ are produced in $e^{+}e^{-}\to \psi(2S)+\gamma$ and $e^{+}e^{-}\to \psi(2S)+f\bar{f}, f=lepton,light quark$, and QED contribution to direct $J/\psi+q\bar{q}$ production with $q=u,d,s$ quark. We find that the QED contribution is huge in the whole phase space region, but can be reduced largely and is in the same order as the QCD contribution when a suitable cut on the angel $\theta_{J/\psi}$ between $J/\psi$ and the $e^{+}e^{-}$ beam is made. In this way, the cross section of $J/\psi+LH$ QCD production %which was predicted theoretical at next-to-leading order QCD together with relativistic correction, can be obtained by subtracting the QED contribution from the experimental measurement on inclusive $J/\psi$ plus light hadrons. To help to remove the QED background, we also calculate the angular and momentum distribution of $J/\psi$ in the QED contribution.