2008 Vol. 32, No. 6
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The littlest Higgs model with T-parity predicts the existence of the neutral, weakly interacting, new gauge boson BH, which can be seen as an attractive dark matter candidate. We study production of the new gauge boson BH via eγ and ep collisions. We find that BH can be abundantly produced via the subprocesses e－γ→L－BH and γq→BHQ, which might give rise to characteristic signals. Some discussions about the SM backgrounds for this kind of signals are also given.
The Babar Collaboration announced two new excited charmed baryons Ξc(3055)+ and Ξc(3123)+. We study their strong decays assuming they are D-wave states. Some assignments are excluded by comparing our numerical results with the experimental values of the total widths of Ξc(3055)+ and Ξc(3123)+. We also suggest some possible decay modes, which will be helpful to
determine the properties of Ξc(3055)+ and Ξc(3123)+
The current quark mass model is adopted to study the phase transition of two-flavor quark matter to more stable three-flavor quark matter in the whole core of a supernova. It shows that the timescale of the process is shorter than 10－8 seconds, that the u- and d-quark masses can be neglected completely in this model, and that the temperature and the total neutrino energies in the core after the conversion increase nearly by 40% and 20% on the average compared with former results, respectively. The last result can further enhance the probability of success for a supernova explosion significantly.
By calculating the excess of the evaporation residue cross sections of the 200Pb
nucleus over that predicted by the standard statistical model as a function of nuclear viscosity coefficient using a Langevin equation combined with a statistical decay model, it is found that high angular momentum not only amplifies the dissipation effects on the excess of the evaporation residue cross sections, but also considerably increases the sensitivity of this excess to the
nuclear viscosity coefficient. These results suggest that on the experimental side, to accurately obtain the information of nuclear dissipation inside the saddle point by measuring the evaporation residue cross section, it had better populate those compound systems with high spins.
In this paper, two injection scenarios with different chopping rate are discussed. The waveforms of the RF voltage are studied and optimized, respectively. Some suggestions are made, concerning chopping and momentum painting of the injected beam. Furthermore, the momentum spread and transverse tune shift are calculated so that the beam aperture and the beam loss can be estimated. Finally, the beam loss with magnet field error is analyzed.
The 9 and 12MeV proton irradiations of the Chinese CMOS Image Sensor in the fluence range from 1×109 to 4×10×10cm－2 and 1×109 to 2×1012cm－2 have been carried out respectively. The color pictures and dark output images are captured, and the average brightness of dark output images is calculated. The anti-irradiation fluence thresholds for 9 and 12~MeV protons are about 4×1010 and 2×1012 cm－2, respectively. These can be explained by the change of the concentrations of irradiation-induced electron-hole pairs and vacancies in the various layers of CMOS image sensor calculated by the TRIM simulation program.
We reported the observation of Y(2175) in φ f0(980) mass spectrum in J/ψ→η π f0(980) with f0(980)→π+π－ and the observation of a broad 1－ resonance of K+
K－ mass in J/ψ→K+ K－ π0. The results from the partial wave analyses of J/ψ→ γπ+π－ and γπ0π0, as well as J/ψ→p K－Λ are also presented.
The cross sections for e+e－→π+π－J/ψ, π+π－ψ(2S), K+K－J/ψ, DD, D0D－+π++c.c., D*D+c.c., and D*D* are measured using data sample collected on or near the Υ(4S) resonance with the Belle detector at KEKB. A peak near 4.25GeV/c2, corresponding to the so called Y(4260), is observed in π+π－J/ψ final state. In addition, there is another cluster of events at around 4.05GeV/c2. Two resonant structures are observed in the π+π－ψ(2S) invariant mass distribution, one at 4361±9±9MeV/c2 with a width of 74±15±10MeV/c2, and another at 4664±11±5MeV/c2 with a width of 48±15± 3MeV/c2. The rich structures observed in all these final states indicate that our understanding of the vector charmonium states above the open charm threshold is still poor, let alone the other possible dynamics such as charmonium hybrids or final state re-scattering and so on.
I review some of the recent experimental results on the so-called XYZ mesons.
We present recent results from BABAR experiment for D0－D0 mixing measurements. Mixing parameters can be measured in different ways using different D0 decay modes, here we discuss the most sensitive analyses such as D0→K+π－ where we had the first evidence of charm mixing, the measurement of the ratio of lifetimes of the decays D0→K+K－ and D0→π+π－ relative to D0→K－π+, the time dependent Dalitz plot analysis of D0→K+π－π0. New limits on CP-violating time-integrated asymmetries in D0→K+K－ and D0→π+π－ are also discussed. The analyses presented are based on 384 fb－1 data collected with the BABAR detector at the PEP-II asymmetric B Factory.
Recently, both BaBar and Belle experiments found evidences of neutral D mixing. In this paper, we discuss the sensitivities of the measurements of D mixing parameters at BESⅢ. With CP tag technique at ψ(3770) peak, the extraction of the strong phase difference in D0 →Kπ decay at BESⅢ are
discussed. We also make an estimate on the measurements of the mixing rate R M by using the coherent data at ψ(3770) peak. The CP violation in D system is predicted with an unobserved level in the Standard Model. Any significant CP violation in the D system indicates the existence of new physics. The sensitivity
of the measurements of CP violation in the D system is estimated in the coherent D decays. Finally, the search for the rare D decays are discussed, in which some of the forbidden decays are smoking gun of new physics.
We present world average values for D0-D0 mixing parameters x and y, CP violation parameters |q/p| and Arg(q/p), and strong phase differences δ and δKππ. These values are calculated by the Heavy Flavor Averaging Group (HFAG)
by performing a global fit to relevant experimental measurements. The results
for x and y differ significantly from zero and are inconsistent with no mixing at the level of 6.7σ. The results for |q/p| and Arg(q/p) are consistent with no CP violation. The strong phase difference δ is less than 45° at 95%C.L.
I give a brief overview of D0-D0 mixing and CP violation in the framework of the standard model. I focus on the theoretical estimate of the D0-D0 mixing parameters and the phenomenological description of several types of CP violation in neutral D-meson decays.
We present a search for new charmonium like states in e+e－ annihilation using the initial-state radiation and the process e+e－J/ψD(*)D(*). The analyses are based on a huge data sample recorded near the Υ(4s) resonance with the Belle detector at the KEKB e+e－ asymmetric-energy collider.
The construction of BESⅢ detector has been finished and the data taking is under plan. Some physics topics on charmonium decays at BESⅢ experiment are discussed in this paper. The measurement of properties of ηc and ηc at BESⅢ is discussed and the expected precision of the measurement is estimated based on BOSS. Also the χcJ decay and the measurement of hyperon decay parameters are mentioned.
We present a preliminary measurement of the B(Ds→μνμ) with the Belle
experiment at the KEKB collider. We select Ds→μνμ decays with a method that provides a high-purity of the selected sample and an absolute measurement of the branching fraction. The results are based on a data sample of 550fb－1 and are compared to similar measurements by other experiments as well as to the predictions of LQCD. We conclude with short prospects for improvements in the accuracy of the measurement.
We have measured the cross section for π+π－ production in two-photon collisions using a data sample with an integrated luminosity of 85.9fb－1 collected with the Belle detector. The f0(980) resonance is observed as a peak in the energy spectrum of the cross section. We also report preliminary results for γγ→π0π0 with two-photon center-of-mass energies ranging from 0.6 to 4.0GeV, based on a 95fb－1 data sample. We find at least four resonant structures including a peak from f0(980). In addition, there is evidence for χc0 production. We also make a preliminary discussion of the angular dependence and cross section ratio of γγ→π+π－ and γγ→π0π0.
Since 1999, the BABAR collaboration has accumulated and studied large samples of tau lepton pairs. The main physics results are reported.
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