15778530
Search for excited charmonium states in e+ e- annihilation at s**(1/2) = 10.6-GeV
We suggest searching for excited charmonium states in e + e - annihilation via double charmonium production at √s = 10.6 GeV with B factories, based on a more complete leading order calculation including both QCD and QED contributions for various processes. In particular, for the C = + states, the x c0 (nP) (n = 2, 3) and η c (mS) (m = 3, 4) may have appreciable potentials to be observed, while for the C = - states, the η c h c production and especially the X c1 h c production might provide opportunities for observing the h c with higher statistics in the future. A brief discussion for the X(3940) observed in the double charmonium production is included.
118620211
Relativistic Correction to Color Octet J/psi Production at Hadron Colliders
The relativistic corrections to the color-octet $J/\psi$ hadroproduction at the Tevatron and LHC are calculated up to $\mathcal{O}(v^2)$ in nonrelativistic QCD factorization frame. The short distance coefficients are obtained by matching full QCD with NRQCD results for the partonic subprocess $g+g\to J/\psi ({}^1S_0^{[8]},{}^3S_1^{[8]}, {}^3P_J^{[8]})+g$, $q+\bar{q}\to J/\psi ({}^1S_0^{[8]},{}^3S_1^{[8]}, {}^3P_J^{[8]})+g$ and $g+q({\bar{q}})\to J/\psi ({}^1S_0^{[8]},{}^3S_1^{[8]}, {}^3P_J^{[8]})+q({\bar{q}})$. The short distance coefficient ratios of relativistic correction to leading order for color-octet states ${^1}S_{0}^{[8]}$, ${^3}S_{1}^{[8]}$, and ${^3}P_{J}^{[8]}$ at large $p_T$ are approximately -5/6, -11/6, and -31/30, respectively, for each subprocess, and it is 1/6 for color-singlet state ${^3}S_{1}^{[1]}$. If the higher order long distance matrix elements are estimated through velocity scaling rule with adopting $v^2=0.23$ and the lower order long distance matrix elements are fixed, the leading order cross sections of color-octet states are reduced by about a factor of $20\sim40%$ at large $p_T$ at both the Tevatron and the LHC. Comparing with QCD radiative corrections to color-octet states, relativistic correction is ignored along with $p_T$ increasing. Using long distance matrix elements extracted from the fit to $J/\psi$ production at the Tevatron, we can find the unpolarization cross sections of $J/\psi$ production at the LHC taking into account both QCD and relativistic corrections are changed by about $20\sim50%$ of that considering only QCD corrections. These results indicate that relativistic corrections may play an important role in $J/\psi$ production at the Tevatron and the LHC.
117075864
Production of J / psi + c anti-c through two photons in e+ e- annihilation
We study the production of $J/\psi+c\bar{c}$ in $e^+e^-$ annihilation through two virtual photons. The cross section is estimated to be 23 fb at $\sqrt{s}=10.6$ GeV, which is smaller by a factor of six than the calculated cross section for the same process but through one virtual photon. As a result, while the annihilation into two photons may be important for certain exclusive production processes, the big gap between the inclusive production cross section $\sigma(e^+e^- \to J/\psi + c\bar{c})\simeq$ 0.9pb observed by Belle and the current nonrelativistic QCD prediction of $\simeq$0.15pb still remains very puzzling. We find, however, as the center-of-mass energy increases ($\sqrt{s}>20$ GeV) the production through two virtual photons $e^+e^- \to 2\gamma^* \to J/\psi + c\bar{c}$ will prevail over that through one virtual photon, because in the former process the photon fragmentation into $J/\psi$ and into the charmed quark pair becomes more important at higher energies.
119479887
S-D mixing and ψ (3770) production in e + e − annihilation and B decay and its radiative transitions
The large decay rate observed by Belle for ${B}^{+}\ensuremath{\rightarrow}\ensuremath{\psi}(3770){K}^{+}$, which is comparable to ${B}^{+}\ensuremath{\rightarrow}\ensuremath{\psi}(3686){K}^{+}$, might indicate either an unexpectedly large S-D mixing angle $|\ensuremath{\theta}|\ensuremath{\approx}{40}^{\ifmmode^\circ\else\textdegree\fi{}}$ or the leading role of the color-octet mechanism in D-wave charmonium production in $B$ decay. By calculating the production rate of $\ensuremath{\psi}(3770)$ in the continuum ${e}^{+}{e}^{\ensuremath{-}}$ annihilation at $\sqrt{s}=10.6\text{ }\text{ }\mathrm{G}\mathrm{e}\mathrm{V}$ with these two possible approaches (i.e., the large S-D mixing and the color-octet mechanism), we show that the measurement for this process at Belle and BABAR may provide a clear cut clarification for the two approaches. In addition, the radiative E1 transition ratio $\ensuremath{\Gamma}[\ensuremath{\psi}(3770)\ensuremath{\rightarrow}\ensuremath{\gamma}{\ensuremath{\chi}}_{c2}]/\ensuremath{\Gamma}[\ensuremath{\psi}(3770)\ensuremath{\rightarrow}\ensuremath{\gamma}{\ensuremath{\chi}}_{c1}]$ may dramatically change from $\ensuremath{\sim}$ 0.04 (for $\ensuremath{\theta}\ensuremath{\approx}{0}^{\ifmmode^\circ\else\textdegree\fi{}}$) to $\ensuremath{\sim}200$ (for $\ensuremath{\theta}\ensuremath{\approx}\ensuremath{-}{40}^{\ifmmode^\circ\else\textdegree\fi{}}$) due to the large S-D interference effect, thus the E1 transition measurement of $\ensuremath{\psi}(3770)$ at Beijing Spectrometer and CLEO-c will also be very useful in clarifying this issue.
122631725
The Study of Color Octet Matrix Elements Through $J/\psi$ and $\Upsilon$ Production in $e^{+}e^{-}$ Annihilation }
The next-to-leading radiative corrections and relativistic corrections to the inclusive heavy quarkonium production in $e^{+}e^{-}\rightarrow J/\psi+LH$ and $e^{+}e^{-}\rightarrow \Upsilon+LH$ are calculated within non-relativistic QCD frame. And the cross section with different the long distance matric elements has been given. We find that the inclusive heavy quarkonium production process in $e^{+}e^{-}$ annihilation can give a strong restrictions on the color octet matrix elements. And the long distance matric elements of P-wave channel for $J/\psi(\psi^\prime)$ would be very small. More measurement of $J/\psi(\psi^\prime)$ and $\Upsilon$ production associated with light hadron at BESIII, Belle, and BelleII can give more information about the color octet matrix elements.
117409239
$J / \psi$ electromagnetic production associated with light hadrons at $B$ factories
The electromagnetic productions of $J \psi$ associated with light hadrons(LH) and leptonic pairs($\mu^+\mu^-$, $\tau^+\tau^-$) at $B$ factories are studied. We find that the direct electromagnetic production cross sections of $J / \psi$($\psi(2S)$) associated with light hadrons is about $0.10(0.04)$ pb. The direct production cross sections of $J / \psi$($\psi(2S)$) associated with $\mu^+\mu^-$ is about $0.056(0.020)$ pb. If we include the contributions from $\psi(2S)$ decay, we can get the prompt cross section $\sigma[e^+e^- \to J/\psi +\mu^+\mu^-]=(0.068 \pm 0.002)$ pb, about $(16 \pm 5) %$ of the Belle data $\sigma[e^+e^- \to J/\psi +X_{non-c\bar c}]=(0.43\pm 0.09\pm 0.09)$ pb, meanwhile the $e^+e^- \to J/\psi +\tau^+\tau^-$ process only contributes $2 %$. The prompt cross section $\sigma[e^+e^- \to J/\psi +Light Hadrons]=(0.121 \pm 0.005)$ pb is about $(28 \pm 8) %$ of the Belle data.
52259853
Low cost concepts to reduce the voltage ripple of a DC power supply
If the gain of current feedback is low, the short term stability of a magnet power supply will be affected by a soft power line. Typically, the step-change and the imbalance of the three phase power line cause the most serious voltage ripple. Usually, voltage feedback with a coupling transformer is considered to reduce the voltage ripple. However, for the high current power supply, the space and cooling problem of the coupling transformer become inconvenient. In this paper, we suggest to use a toroidal core with a compensation winding, working like a DCCT, as the coupling transformer. Then, a high speed detector of the AC line level is developed. It restricts the voltage ripple passing to the coupling transformer. These methods have the advantage of small size, low power consumption and low cost.<<ETX>>
110104367
OPTICAL DESIGN OF THE ENERGY RECOVERY LINAC FEL AT PEKING UNIVERSITY
Peking University is currently designing an Energy Recovery Linac FEL (PKU-ERL-FEL). The system is consisted of a DC-SC photocathode injector, a superconducting linac which is composed of two nine cell TESLA-type cavities, an undulator and beam transport system. The objectives of the PKU-ERL-FEL are providing infrared FEL and building a test-bed for the study of beam dynamics and accelerator technology for energy recovery. In this paper the main parameters of the PKU-ERL-FEL are described and the optical design for the beam transport of PKU-ERL-FEL is presented. The simulation is carried out using the typical particle tracking codes such as elegant.
91176234
DESIGN AND FABRICATION OF A 5-CELL HIGH CURRENT SUPERCONDUCTING CAVITY
Superconducting Energy Recovery Linacs have various applications, such as hard X-ray, electron-ion colliders and electron cooler of ions. The key component for accelerating such high current beams is the superconducting radio frequency cavity. The design of a 1.3 GHz 5-cell high current superconducting cavity has been carried out under the cooperation between Peking University and Argonne National Laboratory. Radio frequency property and damping of the higher order modes of this cavity have been discussed and the final design is presented. Room temperature RF measurements are also described in the paper.
41516045
Earth leakage problem of superconductor magnet system at TLS
Due to the inherent connection structure between the power supplies and the superconducting magnetic coil, the power supplies are seeing each others as loads through the coil. It has been observed in the pilot test at TLS that there is about 300 mA Earth leakage current flowing through the earth leakage protection circuit, which presented an interlock and halted the whole system down. The existence of Earth leakage current may undermine the overall system stability and pose more threat on the electronic system safety. In this paper, the Earth leakage mechanisms are thoroughly examined and measures to conquer the problem are proposed.
117464950
Study on the multi-pass, multi-bunch beam breakup for 9-cell TESLA cavities in ERL *
Generally, Energy Recovery Linac (ERL) needs special designed high current superconducting RF cavities. In this paper, the threshold current of BBU for compact ERL facilities with 9-cell Tesla type cavities are investigated. The results show that it is feasible to adopt 9-cell Tesla cavity for compact ERL test facilities with just a few cavities and beam current around tens mA.