Experimental study of hadron inclusive production in J / psi energy region

title: The sigma pole in J / psi ---> omega pi+ pi-

title: Direct measurements of the branching fractions for inclusive K± and inclusive semileptonic decays of D+ and D0 mesons
abstract: With singly-tagged D ¯ samples selected from the data collected at and around 3.773 GeV with the BESII detector at the BEPC collider, we have measured the branching fractions for the inclusive K ± decays of D + and D 0 mesons, which are BF ( D + → K − X ) = ( 24.7 ± 1.3 ± 1.2 ) % , BF ( D + → K + X ) = ( 6.1 ± 0.9 ± 0.4 ) % , BF ( D 0 → K − X ) = ( 57.8 ± 1.6 ± 3.2 ) % and BF ( D 0 → K + X ) = ( 3.5 ± 0.7 ± 0.3 ) % , respectively. We have also measured the branching fractions for the inclusive semileptonic decays of D + and D 0 mesons to be BF ( D + → e + X ) = ( 15.2 ± 0.9 ± 0.8 ) % and BF ( D 0 → e + X ) = ( 6.3 ± 0.7 ± 0.4 ) % . These yield the ratio of their partial widths to be Γ ( D + → e + X ) / Γ ( D 0 → e + X ) = 0.95 ± 0.12 ± 0.07 .

title: Experimental study of f0(975) in J / psi decays

title: Partial wave analysis of J/psi ---> p anti-p pi0
abstract: Using a sample of 58 million J/{psi} events collected with the BESII detector at the BEPC, more than 100 000 J/{psi}{yields}pp{pi}{sup 0} events are selected, and a detailed partial wave analysis is performed. The branching fraction is determined to be Br(J/{psi}{yields}pp{pi}{sup 0})=(1.33{+-}0.02{+-}0.11)x10{sup -3}. A long-sought missing N*, first observed in J/{psi}{yields}pn{pi}{sup -}, is observed in this decay too, with mass and width of 2040{sub -4}{sup +3}{+-}25 MeV/c{sup 2} and 230{sub -8}{sup +8}{+-}52 MeV/c{sup 2}, respectively. Its spin-parity favors (3/2){sup +}. The masses, widths, and spin parities of other N* states are obtained as well.

title: A side-by-side comparison of Daya Bay antineutrino detectors
abstract: The Daya Bay Reactor Neutrino Experiment is designed to determine precisely the neutrino mixing angle θ_(13) with a sensitivity better than 0.01 in the parameter sin^22θ_(13) at the 90% confidence level. To achieve this goal, the collaboration will build eight functionally identical antineutrino detectors. The first two detectors have been constructed, installed and commissioned in Experimental Hall 1, with steady data-taking beginning September 23, 2011. A comparison of the data collected over the subsequent three months indicates that the detectors are functionally identical, and that detector-related systematic uncertainties are smaller than requirements.

title: Dark matter constraints on the left-right symmetric model with Z(2) symmetry
abstract: In the framework of the left-right symmetric model, we investigate an interesting scenario, in which the so-called vacuum expectation value (VEV)-seesaw problem can be naturally solved with Z(2) symmetry. In such a scenario, we find a pair of stable weakly interacting massive particles (WIMPs), which may be the cold dark matter candidates. However, the WIMP-nucleon cross section is 3-5 orders of magnitude above the present upper bounds from the direct dark matter detection experiments for m similar to 10(2)-10(4) GeV. As a result, the relic number density of two stable particles has to be strongly suppressed to a very small level. Nevertheless, our analysis shows that this scenario cannot provide very large annihilation cross sections so as to give the desired relic abundance except for the resonance case. Only for the case if the rotation curves of disk galaxies are explained by the modified Newtonian dynamics (MOND), the stable WIMPs could be as the candidates of cold dark matter.

title: Higgs-pair production in littlest Higgs model with T parity
abstract: The Higgs-pair production process at the CERN Large Hadron Collider, which will provide a way to test the Higgs boson self-coupling, may be sensitive to new physics. In the framework of the littlest Higgs model with T parity, such Higgs-pair production can proceed through additional loop diagrams, and thus the production rate can be quite different from the standard model prediction. Our calculations show that, due to the loop contributions of both T-even and T-odd quarks predicted in this model, the production rate can be significantly enhanced relative to the standard model prediction and also can be larger than the production rate in the minimal supersymmetric model. Also, we find that the T-odd quark contributions, which were not included in a previous study, are equally important compared with the T-even quark contributions.

title: Gauge-singlet dark matter in a left-right symmetric model with spontaneous CP violation
abstract: We propose a dark matter (DM) scenario in an extension of a left-right symmetric model with a gauge-singlet scalar field. The gauge-singlet scalar can automatically become a DM candidate, provided that both P and CP symmetries are only broken spontaneously. Thus no extra discrete symmetries are needed to make the DM candidate stable. After constraining the model parameters from the observed relic DM density we make predictions for direct detection experiments. We show that for some parameter range, the predicted weakly interacting massive particle-nucleon elastic scattering cross section can reach the current experimental upper bound, which can be tested by the experiments in the near future.

title: What if bb does not dominate the decay of the Higgs-like boson?
abstract: The dominant decay mode of standard model Higgs at 126 GeV $b\bar{b}$ suffers from severe SM background at the LHC even in associated productions $Wh_{\rm SM}$ or $Z h_{\rm SM}$. The precision measurement of BR($\phi\to b\bar{b})$ requires more data to reduce its large error bar. We investigate the possibility of this channel with largest uncertainty not dominating the decay of Higgs-like boson discovered at the LHC. In such scenarios, the Higgs signal shows highly suppressed $b\bar{b}$, slightly reduced $\tau^{+}\tau^{-}$ and moderately enhanced gauge bosons comparing with the SM predictions. The model requires two different sources of electroweak symmetry breaking and radiative correction to $m_{b}$ strongly enhanced. However, large reduction in $b\bar{b}$ usually results large enhancement in $\tau^{+}\tau^{-}$ mode in particular. The reduction of $\tau^{+}\tau^{-}$ therefore implies that a new decay mode is inevitable. We find that a non-decoupling MSSM Higgs decay into lighter Higgs $H\to  may fit the signature. Here, MSSM $H$ is identified as the 126 GeV resonance while $h$ is below $M_{H}/2$ and can evade the direct search bound at LEPII and Tevatron. R$ symmetry breaking effects mediated by strong interaction can strongly enhance radiative corrections in $m_b$. However, the scenario can only be realized in highly fine-tuned parameter region where $G_{Hhh}$ is tiny. Nevertheless, we discuss the discovery potential of this highly fine-tuned $H\to hh$ at the LHC.

title: Study of a prototype water Cherenkov detector for the Daya Bay neutrino experiment
abstract: The Daya Bay reactor neutrino experiment is designed to precisely measure the neutrino mixing angle theta(13). The anti-neutrino detectors are shielded by highly purified water against radioactivity and spallation neutrons from surrounding rocks. The water also serves as a Cherenkov detector to tag cosmic-ray muons, which induce main backgrounds. In order to study water purification and details of the detector response, a prototype water Cherenkov detector is constructed at the Institute of High Energy Physics (IHEP), Beijing. The detector is divided by Tyvek into two sections and viewed by two 8 in. photomultipliers. Cosmic-ray muons are used for detector response studies and a Monte Carlo simulation based on the Geant4 package shows good agreement with the experimental data.