An energy signature for very deep underground muons observed by the LVD experiment

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: 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: 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: Measurement of the polarization amplitudes and triple product asymmetries in the B-s(0) -> phi phi decay
abstract: Using 1.0 fb^{-1} of pp collision data collected at a centre-of-mass energy of sqrt{s}=7 TeV with the LHCb detector, measurements of the polarization amplitudes, strong phase difference and triple product asymmetries in the B_s^0 -> phi phi decay mode are presented. The measured values are |A_0|^2 = 0.365 +- 0.022 (stat) +- 0.012 (syst), |A_perp|^2 = 0.291 +- 0.024 (stat) +- 0.010 (syst), cos(delta_parallel) = -0.844 +- 0.068 (stat) +- 0.029 (syst), A_U = -0.055 +- 0.036 (stat) +- 0.018 (syst), A_V = 0.010 +- 0.036 (stat) +- 0.018 (syst) .

title: Measurement of CP violation in the phase space of $B^{\pm} \to K^{\pm} \pi^{+} \pi^{-}$ and $B^{\pm} \to K^{\pm} K^{+} K^{-}$ decays
abstract: The charmless decays $B^{\pm}\to K^{\pm}\pi^+\pi^-$ and $B^{\pm}\to K^{\pm}K^+K^-$ are reconstructed using data, corresponding to an integrated luminosity of 1.0 fb$^{-1}$, collected by LHCb in 2011. The inclusive charge asymmetries of these modes are measured as $A_{C\!P}(B^{\pm}\to K^{\pm}\pi^+\pi^-) = 0.032 \pm 0.008 \stat \pm 0.004 \syst \pm 0.007 (J\psi K^{\pm})$ and $A_{C\!P}(B^{\pm}\to K^{\pm}K^+K^-) = -0.043 \pm 0.009 \stat \pm 0.003 \syst \pm 0.007 (J\psi K^{\pm})$, where the third uncertainty is due to the $C\!P$ asymmetry of the $B^{\pm}\to J\psi K^{\pm}$ reference mode. The significance of $A_{C\!P}(B^{\pm}\to K^{\pm}K^+K^-)$ exceeds three standard deviations and is the first evidence of an inclusive $C\!P$ asymmetry in charmless three-body $B$ decays. In addition to the inclusive $C\!P$ asymmetries, larger asymmetries are observed in localised regions of phase space.

title: Search for the rare decay $D^0 \to \mu^+ \mu^-$
abstract: A search for the rare decay $D^0 \to \mu^+ \mu^-$is performed using a data sample, corresponding to an integrated luminosity of 0.9 fb$^{-1}$, of $pp$ collisions collected at a centre-of-mass energy of 7 TeV by the LHCb experiment. The observed number of events is consistent with the background expectations and corresponds to an upper limit of \mbox{${\cal B}(D^0 \to \mu^+ \mu^-) < 6.2(7.6) \times 10^{-9}$} at \mbox{90%} \mbox{(95%)} confidence level. This result represents an improvement of more than a factor twenty with respect to previous measurements.

title: Amplitude analysis and the branching fraction measurement of $\bar{B}^0_s \to J/\psi K^+K^-$
abstract: An amplitude analysis of the final state structure in the Bs0→J/ψK+K- decay mode is performed using 1.0  fb-1 of data collected by the LHCb experiment in 7 TeV center-of-mass energy pp collisions produced by the LHC. A modified Dalitz plot analysis of the final state is performed using both the invariant mass spectra and the decay angular distributions. Resonant structures are observed in the K+K- mass spectrum as well as a significant non-resonant S-wave contribution over the entire K+K- mass range. The largest resonant component is the ϕ(1020), accompanied by f0(980), f2′(1525), and four additional resonances. The overall branching fraction is measured to be B(Bs0→J/ψK+K-)=(7.70±0.08±0.39±0.60)×10-4, where the first uncertainty is statistical, the second systematic, and the third due to the ratio of the number of Bs0 to B- mesons produced. The mass and width of the f2′(1525) are measured to be 1522.2±2.8-2.0+5.3  MeV and 84±6-5+10  MeV, respectively. The final state fractions of the other resonant states are also reported.

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.