Xue-Qian Li

CONSTRAINTS ON SCALAR DARK MATTER FROM DIRECT EXPERIMENTAL SEARCHES

The standard model (SM) plus a real gauge-singlet scalar field dubbed darkon (SM+D) is the simplest model possessing a weakly interacting massive particle (WIMP) dark-matter candidate. The upper limits for the WIMP-nucleon elastic cross section as a function of WIMP mass from the recent XENON10 and CDMS II experiments rule out darkon mass ranges from 10 to (50, 70, 75) GeV for Higgs-boson masses of (120, 200, 350) GeV, respectively. This may exclude the possibility of the darkon providing an explanation for the gamma-ray excess observed in the EGRET data. We show that by extending the SM+D to a two-Higgs-doublet model plus a darkon the experimental constraints on the WIMP-nucleon interactions can be circumvented due to suppression occurring at some values of the product tan{alpha}tan{beta}, with {alpha} being the neutral-Higgs mixing angle and tan{beta} the ratio of vacuum expectation values of the Higgs doublets. We also comment on the implication of the darkon model for Higgs searches at the LHC.

Unparticle physics effects on D0–D0¯ mixing

Abstract The mixing of K 0 – K 0 ¯ , D 0 – D 0 ¯ and B ( s ) 0 – B ( s ) 0 ¯ provides a sensitive probe to explore new physics beyond the Standard Model. The scale invariant unparticle physics recently proposed by Georgi can induce flavor-changing neutral current and contribute to the mixing at tree level. We investigate the unparticle effects on B 0 – B 0 ¯ and D 0 – D 0 ¯ mixing. Especially, the newly observed D 0 – D 0 ¯ mixing sets the most stringent constraints on the coupling of the unparticle to quarks.

The simplest dark-matter model, CDMS II results, and Higgs detection at LHC

Abstract The direct-search experiment for dark matter performed by the CDMS II Collaboration has observed two candidate events. Although these events cannot be interpreted as significant evidence for the presence of weakly interacting massive particle (WIMP) dark matter (DM), the total CDMS II data have led to an improved upper-limit on the WIMP-nucleon spin-independent cross-section. We study some implications of these results for the simplest WIMP DM model, the SM+D, which extends the standard model (SM) by the addition of a real SM-singlet scalar field dubbed darkon to play the role of the DM. We find that, although the CDMS II data rule out a sizable portion of parameter space of the model, a large part of the parameter space is still allowed. We obtain strong correlations among the darkon mass, darkon–nucleon cross-section, mass of the Higgs boson, and branching ratio of its invisible decay. We point out that measurements of the Higgs invisible branching-ratio at the LHC can lift some possible ambiguities in determining the darkon mass from direct DM searches.

Introduction to the CDEX experiment

It is believed that weakly interacting massive particles (WIMPs) are candidates for dark matter (DM) in our universe which come from outer space and might interact with the standard model (SM) matter of our detectors on the earth. Many collaborations in the world are carrying out various experiments to directly detect DM particles. China Jinping underground Laboratory (CJPL) is the deepest underground laboratory in the world and provides a very promising environment for DM search. China Dark matter EXperiment (CDEX) is going to directly detect the WIMP flux with high sensitivity in the low WIMP-mass region. Both CJPL and CDEX have achieved a remarkable progress in recent three years. CDEX employs a point-contact germanium (PCGe) semi-conductor detector whose energy threshold is less than 300 eV. In this report we present the measurement results of muon flux, monitoring of radioactivity and radon concentration carried out in CJPL, as well describing the structure and performance of the 1 kg-PCGe detector in CDEX-1 and 10 kg-PCGe detector array in CDEX-10 including the detectors, electronics, shielding and cooling systems. Finally we discuss the physics goals of CDEX-1, CDEX-10 and the future CDEX-1T experiments.

SCALAR DARK MATTER EFFECTS IN HIGGS AND TOP QUARK DECAYS

We study possible observational effects of scalar dark matter, the darkon D, in Higgs h and top quark t decay processes, h → DD and t → cDD in the minimal Standard Model (SM) and its two Higgs doublet model (THDM) extension supplemented with a SM singlet darkon scalar field D. We find that the darkon D can have a mass in the range of sub-GeV to several tens of GeV, interesting for LHC and ILC colliders, to produce the required dark matter relic density. In the SM with a darkon, t → cDD only occurs at loop level giving a very small rate, while the rate for Higgs decay h → DD can be large. In THDM III with a darkon, where tree level flavor changing neutral current (FCNC) interaction exists, a sizable rate for t → cDD is also possible.

Effect of stealthy liposomal topotecan plus amlodipine on the multidrug-resistant leukaemia cells in vitro and xenograft in mice

Background  Multidrug resistance (MDR) is a major obstacle to successful cancer chemotherapy as the over‐expressed MDR protein acts as an efflux pump, which leads to a reduction in the uptake of the anticancer agent by tumour cells. We combined topotecan and amlodipine together into the stealthy liposomes, in which amlodipine was applied as a MDR reversing agent to overcome the resistance.

Spectra of the lightest baryons containing two heavy quarks in a potential model

The spectra of baryons which include two heavy quarks can be treated as a two-body system, where the two heavy quarks constitute a bosonic diquark. We derive the effective potential between the light quark and the heavy diquark in terms of the Bethe-Salpeter equation. To obtain the spectra, several serious problems need to be solved: (1) the operator ordering, (2) the errors caused by the nonrelativistic expansion, (3) spin-spin coupling, and (4) the mixing between the scalar-diquark-baryon and vector-diquark-baryon. In this work we take reasonable approaches to deal with them.

The first candidate for chiral nuclei in the A~80 mass region: 80Br

Abstract Excited states of 80Br have been investigated via the 76Ge(11B, α 3 n ) and 76Ge(7Li, 3n) reactions and a new Δ I = 1 band has been identified which resides ∼ 400 keV above the yrast band. Based on the experimental results and their comparison with the triaxial particle rotor model calculated ones, a chiral character of the two bands within the π g 9 / 2 ⊗ ν g 9 / 2 configuration is proposed, which provides the first evidence for chirality in the A ∼ 80 region.

Neutrino decay as a possible interpretation of the MiniBooNE observation with unparticle scenario

In a new measurement on neutrino oscillations, νμ→νe, the MiniBooNE Collaboration observes an excess of electron-like events at low energy and the phenomenon may demand an explanation that obviously is beyond the oscillation picture. We propose that the heavier neutrino, ν2, decaying into a lighter one, ν1, via the transition process νμ→νe+X, where X denotes any light products, could be a natural mechanism. The theoretical model we employ here is the unparticle scenario established by Georgi. We have studied two particular modes

Fourth-generation signatures in D0-;D̄0 mixing and rare D decays

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