STUDYING ENERGETIC MUONS AT THE LVD SETUP

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: 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 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: 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: Particle polarization in inclusive reactions

title: Study of forward Z + jet production in pp collisions at $ \sqrt{s} $ = 7 TeV
abstract: A bstractA measurement of the Z(→ μ+μ−) + jet production cross-section in pp collisions at a centre-of-mass energy $ \sqrt{s} $ = 7 TeV is presented. The analysis is based on an integrated luminosity of 1.0 fb−1 recorded by the LHCb experiment. Results are shown with two jet transverse momentum thresholds, 10 and 20 GeV, for both the overall cross-section within the fiducial volume, and for six differential cross-section measurements. The fiducial volume requires that both the jet and the muons from the Z boson decay are produced in the forward direction (2.0 < η < 4.5). The results show good agreement with theoretical predictions at the second-order expansion in the coupling of the strong interaction.

title: Measurement of b-hadron branching fractions for two-body decays into charmless charged hadrons
abstract: A bstractBased on data corresponding to an integrated luminosity of 0.37 fb−1 collected by the LHCb experiment in 2011, the following ratios of branching fractions are measured:$ \begin{array}{*{20}{c}} {{{{\mathcal{B}\left( {B^0 \to } \right)}} \left/ {{\mathcal{B}\left( {B^0 \to {K^{+}}{\pi^{-}}} \right)}} \right.}=0.262\pm 0.009\pm 0.017,} \\ {\left( {{f_s \left/ {f_d } \right.}} \right)\cdot {{{\mathcal{B}\left( {B_s^0\to {K^{+}}{K^{-}}} \right)}} \left/ {{\mathcal{B}\left( {B^0 \to {K^{+}}{\pi^{-}}} \right)}} \right.}=0.316\pm 0.009\pm 0.019,} \\ {\left( {{f_s \left/ {f_d } \right.}} \right)\cdot {{{\mathcal{B}\left( {B_s^0\to {\pi^{+}}{K^{-}}} \right)}} \left/ {{\mathcal{B}\left( {B^0 \to {K^{+}}{\pi^{-}}} \right)}} \right.}=0.074\pm 0.006\pm 0.006,} \\ {\left( {{f_d \left/ {f_s } \right.}} \right)\cdot {{{\mathcal{B}\left( {B^0 \to {K^{+}}{K^{-}}} \right)}} \left/ {{\mathcal{B}\left( {B_s^0\to {K^{+}}{K^{-}}} \right)}} \right.}=0.018_{-0.007}^{+0.008}\pm 0.009,} \\ {\left( {{f_s \left/ {f_d } \right.}} \right)\cdot {{{\mathcal{B}\left( {B_s^0\to {\pi^{+}}{\pi^{-}}} \right)}} \left/ {{\mathcal{B}\left( {B^0 \to } \right)}} \right.}=0.050_{-0.009}^{+0.011}\pm 0.004,} \\ {{{{\mathcal{B}\left( {\Lambda_b^0\to p{\pi^{-}}} \right)}} \left/ {{\mathcal{B}\left( {\Lambda_b^0\to p{K^{-}}} \right)}} \right.}=0.86\pm 0.08\pm 0.05,} \\ \end{array} $where the first uncertainties are statistical and the second systematic. Using the current world average of $ \mathcal{B}\left( {B^0 \to {K^{+}}{\pi^{-}}} \right) $ and the ratio of the strange to light neutral B meson production fs/fd measured by LHCb, we obtain:$ \begin{array}{*{20}{c}} {\mathcal{B}\left( {B^0 \to } \right)=\left( {5.08\pm 0.17\pm 0.37} \right)\times {10^{-6 }},} \\ {\mathcal{B}\left( {B_s^0\to {K^{+}}{K^{-}}} \right)=\left( {23.0\pm 0.7\pm 2.3} \right)\times {10^{-6 }},} \\ {\mathcal{B}\left( {B_s^0\to {\pi^{+}}{K^{-}}} \right)=\left( {5.4\pm 0.4\pm 0.6} \right)\times {10^{-6 }},} \\ {\mathcal{B}\left( {B^0 \to {K^{+}}{K^{-}}} \right)=\left( {0.11_{-0.04}^{+0.05}\pm 0.06} \right)\times {10^{-6 }},} \\ {\mathcal{B}\left( {B_s^0\to {\pi^{+}}{\pi^{-}}} \right)=\left( {0.95_{-0.17}^{+0.21}\pm 0.13} \right)\times {10^{-6 }}. $ is observed for the first time with a significance of more than 5σ.

title: Measurement of the Ds+ - Ds- production asymmetry in 7 TeV pp collisions
abstract: Article history: Received 4 May 2012 Received in revised form 30 May 2012  W.-D. Schlatter Heavy quark production in 7 TeV centre-of-mass energy pp collisions at the LHC is not necessarily flavour symmetric. The production asymmetry, AP, between D+s and D−s mesons is studied using the φπ± decay mode in a data sample of 1.0 fb−1 collected with the LHCb detector. The difference between π+ and π− detection efficiencies is determined using the ratios of fully reconstructed to partially reconstructed D∗± decays. The overall production asymmetry in the D±s rapidity region 2.0 to 4.5 with transverse momentum larger than 2 GeV is measured to be AP = (−0.33 ± 0.22 ± 0.10)%. This result can constrain models of heavy flavour production.

title: First measurement of the CP-violating phase in $B_s^0 \to \phi \phi$ decays
abstract: A first flavour-tagged measurement of the time-dependent CP-violating asymmetry in $B_s^0 \to \phi\phi$ decays is presented. In this decay channel, the CP-violating weak phase arises due to CP violation in the interference between $B_s^0$-$\bar{B}_s^0$ mixing and the $b \to s \bar{s} s $ gluonic penguin decay amplitude. Using a sample of $pp$ collision data corresponding to an integrated luminosity of $1.0\; fb^{-1}$ and collected at a centre-of-mass energy of $7 \rm TeV$ with the LHCb detector, $880\ \B_s^0 \to \phi\phi$ signal decays are obtained. The CP-violating phase is measured to be in the interval [-2.46, -0.76] \rm rad$ at 68% confidence level. The p-value of the Standard Model prediction is 16%.

title: Production of high-energy muons in extensive air showers from primary el rays
abstract: The primary mechanism for the production of high-energy muons (E/sub / > 5 TeV) in extensive air showers from primary el rays is the production of muon pairs by shower photons in the field of a nucleus.