17109568
Inclusive charmonium production via double $c \bar{c}$ in $e^{+} e^{-}$ annihilation
Motivated by the recent observation of double charm quark pair production by the Belle Collaboration, we calculate the complete ${\cal O}(\alpha_{s}^{2})$ inclusive production cross sections for $\eta_{c}$, $J/\psi$, and $\chi_{cJ}$(J=0, 1, 2) plus $c\bar{c}$ in $e^+ e^-$ annihilation through a virtual photon. We consider both color-singlet and color-octet contributions, and give the analytical expressions for these cross sections. The complete color-singlet calculations are compared with the approximate fragmentation calculations as functions of the center-of-mass energy $\sqrt{s}$. We find that most of the fragmentation results substantially overestimate the cross sections (e.g. by a factor of $\sim$4 for $\chi_{c1}$ and $\chi_{c2}$) at the Belle and BaBar energy $\sqrt{s}=10.6$GeV. The fragmentation results become a good approximation only when $\sqrt{s}$ is higher than about 100GeV. We further calculate the color-octet contributions to these cross sections with analytical expressions. We find that while the color-octet contribution to $J/\psi$ inclusive production via double charm is negligible (only about 3%), the color-octet contributions to $\chi_{c1}$ and $\chi_{c2}$ can be significant.
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.
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.
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.
124097178
Neutrino Oscillation and CP Violation in Low Energy Phenomenology of an SUSY Model
Neutrino oscillation and CP violation effects are discussed in an SUSY model proposed in Ref. [1]. The oscillation probabilities expected by this model in short baseline and long baseline neutrino oscillation experiments are calculated. The small conversion probability is predicted for all or oscillations. However, large long baseline oscillation probability is predicted, which could be observed in future long baseline experiments.
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>>
120411181
Recent progress in techniques utilized for particle accelerator
Particle accelerators are widely used in scientific research and industry. Recently, techniques utilized for accelerator are developed rapidly in China. We briefly review the recent progress in this field and primarily focus on superconducting RF, innovative structures for particle production and acceleration and beam diagnosis. Several advanced compact user facilities are also introduced.
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.
110332574
Precision current monitor system for the power supplies at SRRC
At SRRC, a precision output current monitoring system is installed to monitor the output performance of all the booster/storage ring power supplies. Accurate DC current transformers (DCCTs) are attached to the output terminal of every power supply system. Each transformer's gain/offset are carefully calibrated against a high precision current source and approximated using high-order polynomial curve fitting. The output of each DCCT is connected to a multi-channel data logger for realtime data collection, the collected data are calibrated using the interpolated DCCT gain/offset value. A PC station is set up to serve as host to store the current output for real-time monitoring. This monitoring system provides a precise real-time database for rapid fault diagnosing whenever there is malfunction of the beam operation.
164614043
Analysis and Compensator Design of Magnet Correction Power Supply
POWER SUPPLY Yong-Seng Wong , Kuo-Bin Liu, Jhao-Cyuan Huang NSRRC, Hsinchu 30076, Taiwan . Abstract This paper presents a new method for the analysis and design of compensators for magnet correction (MC) power supply. The system has to need controllers to satisfy required gain and phase margin specifications and compensator by adding to circuit controller and switch. The gain-phase margin tester method can transform of the controller and find solutions on the figure. According to circuit frequency response and transfer function by theory analysis and simulation design new method compensators to improved anti-disturbance and stability of the system.