MUON-INDUCED NEUTRON PRODUCTION AND DETECTION WITH GEANT4 AND FLUKA

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: 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: Particle polarization in inclusive reactions

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: Measurement of the D ± production asymmetry in 7 TeV pp collisions
abstract: Heavy quark production in 7 TeV centre-of-mass energy pp collisions at the LHC is not necessarily flavour symmetric. The production asymmetry, A(P), between D-s(+) and D-s(-) mesons is studied using the phi pi(+/-) decay mode in a data sample of 1.0 fb(-1) collected with the LHCb detector. The difference between pi(+) and pi(-) 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 A(P) = (-0.33 +/- 0.22 +/- 0.10)%. This result can constrain models of heavy flavour production.

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.

title: Precision measurement of D meson mass differences
abstract: A bstractUsing three- and four-body decays of D mesons produced in semileptonic b-hadron decays, precision measurements of D meson mass differences are made together with a measurement of the D0 mass. The measurements are based on a dataset corresponding to an integrated luminosity of 1.0 fb−1 collected in pp collisions at 7 TeV. Using the decay D0 → K+K−K−π+, the D0 mass is measured to be
$ M\left( } \right)={{{1864.75\pm 0.15\left( {\mathrm{stat}} \right)\pm 0.11\left( {\mathrm{syst}} \right)\mathrm{MeV}}} \left/ {{{c^2}}} \right.}. $
 The mass differences
 $ \begin{array}{*{20}{c}} {{{{M\left( } \right)-M\left( } \right)=4.76\pm 0.12\left( {\mathrm{stat}} \right)\pm 0.07\left( {\mathrm{syst}} \right)\mathrm{MeV}}} \left/ {{{c^2}}} \right.},} \hfill \\ {{{{M\left( } \right)-M\left( } \right)=98.68\pm 0.03\left( {\mathrm{stat}} \right)\pm 0.04\left( {\mathrm{syst}} \right)\mathrm{MeV}}} \left/ {{{c^2}}} \right.}} \hfill \\ \end{array} $
 are measured using the D0 → K+K−π+π− and $ D_{(s)}^{+}\to {K^{+}}{K^{-}}{\pi^{+}} $ modes.

title: Searches for violation of lepton flavour and baryon number in tau lepton decays at LHCb
abstract: Searches for the lepton flavour violating decay tau(-) -> mu(-)mu(+)mu(-) and the lepton flavour and baryon number violating decays tau(-) -> (p) over bar mu(+)mu(-) and tau(-) -> p mu(-)mu(-) have been carried out using proton-proton collision data, corresponding to an integrated luminosity of 1.0 fb(-1), taken by the LHCb experiment at root s = 7 TeV. No evidence has been found for any signal, and limits have been set at 90% confidence level on the branching fractions: B(tau(-) -> mu(-)mu(+)mu(-) mu(+)mu(-)) p mu(-)mu(-)) (p) over bar mu(+)mu(-) and tau(-) -> p mu(-)mu(-) decay modes represent the first direct experimental limits on these channels.

title: First measurement of the charge asymmetry in beauty-quark pair production.
abstract: The difference in the angular distributions between beauty quarks and antiquarks, referred to as the charge asymmetry, is measured for the first time in bb pair production at a hadron collider. The data used correspond to an integrated luminosity of 1.0 fb(-1) collected at 7 TeV center-of-mass energy in proton-proton collisions with the LHCb detector. The measurement is performed in three regions of the invariant mass of the bb system. The results obtained are A(C)(bb))(40 105 GeV/c(2)) = 1.6 ± 1.7 ± 0.6%, where A(C)(bb)) is defined as the asymmetry in the difference in rapidity between jets formed from the beauty quark and antiquark, where in each case the first uncertainty is statistical and the second systematic. The beauty jets are required to satisfy 2 < η < 4, E(T) >20 GeV, and have an opening angle in the transverse plane Δ ϕ > 2.6 rad. These measurements are consistent with the predictions of the standard model.