A study of the LSD-2 experiment background

title: The ZEPLIN-III dark matter detector: Performance study using an end-to-end simulation tool
abstract: We present results from a GEANT4-based Monte Carlo tool for end-to-end simulations of the ZEPLIN-III dark matter experiment. ZEPLIN-III is a two-phase detector which measures both the scintillation light and the ionisation charge generated in liquid xenon by interacting particles and radiation. The software models the instrument response to radioactive backgrounds and calibration sources, including the generation, ray-tracing and detection of the primary and secondary scintillations in liquid and gaseous xenon, and subsequent processing by data acquisition electronics. A flexible user interface allows easy modification of detector parameters at run time. Realistic datasets can be produced to help with data analysis, an example of which is the position reconstruction algorithm developed from simulated data. We present a range of simulation results confirming the original design sensitivity of a few times 10−8 pb to the WIMP-nucleon cross-section.

title: Particle polarization in inclusive reactions

title: Progress report from the UK Dark Matter search at Boulby Mine
abstract: The UK Dark Matter Collaboration is currently running a series of scintillation devices at the Boulby mine in North Yorkshire to search for the neutralino, the hypothetical WIMP solution to the dark matter problem. Results of the current NaI(T1) detector array will be discussed, illustrating a population of events of unknown origin. Diagnostic tests performed to investigate the origin of these anomalous events will be outlined, including alpha, beta and neutron calibrations.

title: Muon-induced background in the EDELWEISS dark matter search
abstract: A dedicated analysis of the muon-induced background in the EDELWEISS dark matter search has been performed on a data set acquired in 2009 and 2010. The total muon flux underground in the Laboratoire Souterrain de Modane (LSM) was measured to be Φ μ = ( 5.4 ± 0.2 - 0.9 + 0.5 )  muons/m 2 /d. The modular design of the μ -veto system allows the reconstruction of the muon trajectory and hence the determination of the angular dependent muon flux in LSM. The results are in good agreement with both MC simulations and earlier measurements. Synchronization of the μ -veto system with the phonon and ionization signals of the Ge detector array allowed identification of muon-induced events. Rates for all muon-induced events Γ μ = ( 0.172 ± 0.012 ) evts / ( kg d ) and of WIMP-like events Γ μ – n = 0.008 - 0.004 + 0.005 evts / ( kg d ) were extracted. After vetoing, the remaining rate of accepted muon-induced neutrons in the EDELWEISS-II dark matter search was determined to be Γ irred μ – n 6 · 10 - 4 evts / ( kg d ) at 90% C.L. Based on these results, the muon-induced background expectation for an anticipated exposure of 3000 kg d for EDELWEISS-III is N 3000 kg d μ – n 0.6 events.

title: The potential of liquid xenon for WIMP search: the ZEPLIN diagnostic array
abstract: A Liquid Xenon based WIMP detector diagnostic array is currently developed by the UKDMC with the help of international collaborators. After a brief reminder on the detection principle in Liquid Xenon, the individual detectors will be described. ZEPLIN I, a detector with a 4 kg fiducial mass with a background discrimination based on Pulse Shape Analysis, is already underground and starting operation. Two setups with improved background discrimination tools (as the ionisation is also recorded) are designed and scheduled to move underground in the second half of 2001. Both of them, ZEPLIN II and ZEPLIN III, are predicted to be sensitive to rate of 0.1–0.01 events/kg/day within 2 years of data taking. Furthermore, new ideas for lower background readout devices are studied, in order to avoid the use of PhotoMultiplier Tubes (PMTs).

title: Observation of $B^0_s\rightarrow\chi_{c1}\phi$ decay and study of $B^0\rightarrow\chi_{c1,2}K^{*0}$ decays
abstract: The first observation of the decay $B^0_s\rightarrow\chi_{c1}\phi$ and a study of $B^0\rightarrow\chi_{c1,2}K^{*0}$ decays are presented. The analysis is performed using a dataset, corresponding to an integrated luminosity of 1.0 fb$^{-1}$, collected by the LHCb experiment in pp collisions at a centre-of-mass energy of 7 TeV. The following ratios of branching fractions are measured: \begin{equation*} \begin{array}{lll} \dfrac{\cal{B}(B^0_s\rightarrow\chi_{c1}\phi)}{\cal{B}(B^0_s\rightarrow J/\psi\phi)} &=& (18.9 \pm1.8\,(stat)\pm1.3\,(syst)\pm0.8\,(\cal{B})) \times 10^{-2}, \nonumber \\ \noalign{\vskip 3pt} \dfrac{\cal{B}(B^0\rightarrow\chi_{c1}K^{*0})}{\cal{B}(B^0\rightarrow J/\psiK^{*0})} &=& (19.8 \pm1.1\,(stat)\pm1.2\,(syst)\pm0.9\,(\cal{B})) \times 10^{-2}, \nonumber \\ \noalign{\vskip 3pt} \dfrac{\cal{B}(B^0\rightarrow\chi_{c2}K^{*0})}{\cal{B}(B^0\rightarrow\chi_{c 1}K^{*0})} &=& (17.1 \pm5.0\,(stat)\pm1.7\,(syst)\pm1.1\,(\cal{B})) \times 10^{-2}, \nonumber \\ \noalign{\vskip 3pt} \end{array} \end{equation*} \noindent where the third uncertainty is due to the limited knowledge of the branching fractions of ${\chi_{c}\rightarrow J/\psi \gamma}$ modes.

title: Unified description of hadronic and leptonic degrees of freedom in a superstring model involving supercurrent conditions

title: Search for CP violation in the decay $D^+ \to \pi^-\pi^+\pi^+$
abstract: A search for CP violation in the phase space of the decay $D^+\to\pi^-\pi^+\pi^+$ is reported using $pp$ collision data, corresponding to an integrated luminosity of 1.0 fb$^{-1}$, collected by the LHCb experiment at a centre-of-mass energy of 7 TeV. The Dalitz plot distributions for $3.1\times 10^6$ $D^+$ and $D^-$ candidates are compared with binned and unbinned model-independent techniques. No evidence for CP violation is found.

title: Study of beauty hadron decays into pairs of charm hadrons
abstract: First observations of the decays Λb 0 → Λc +D(s) - are reported using data corresponding to an integrated luminosity of 3fb-1 collected at 7 and 8 TeV center-of-mass energies in proton-proton collisions with the LHCb detector. In addition, the most precise measurement of the branching fraction B(Bs 0→D+Ds -) is made and a search is performed for the decays B(s) 0→Λc +Λc -. The results obtained are B(Λb 0→Λc +D-)/ B(Λb 0→Λc +D s -)=0.042±0.003(stat)±0.003(syst), [B(Λb 0→Λc +D s -)/B(B0→D+D s -)]/[B(Λb 0→Λ c +π-)/B(B0→D +π-)]=0.96±0.02(stat)±0.06(syst),B(B s 0→D+Ds -)/ B(B0→D+Ds -)=0. 038±0.004(stat)±0.003(syst),B(B0→Λ c +Λc -)/B(B , B(Bs 0→Λc +Λ c -)/B(Bs 0→D+D s -)<0.30[95%C.L.]. Measurement of the mass of the Λb 0 baryon relative to the B0 meson gives M(Λb 0)-M(B0)=339. 72±0.24(stat)±0.18(syst)MeV/c2. This result provides the most precise measurement of the mass of the Λb 0 baryon to date.

title: Observation of photon polarization in the b→sγ transition.
abstract: This Letter presents a study of the flavor-changing neutral current radiative B±→K±π∓π±γ decays performed using data collected in proton-proton collisions with the LHCb detector at 7 and 8 TeV center-of-mass energies. In this sample, corresponding to an integrated luminosity of 3  fb-1, nearly 14 000 signal events are reconstructed and selected, containing all possible intermediate resonances with a K±π∓π± final state in the [1.1,1.9]  GeV/c2 mass range. The distribution of the angle of the photon direction with respect to the plane defined by the final-state hadrons in their rest frame is studied in intervals of K±π∓π± mass and the asymmetry between the number of signal events found on each side of the plane is obtained. The first direct observation of the photon polarization in the b→sγ transition is reported with a significance of 5.2σ.