TORCH is a novel time-of-flight detector, designed to provide charged particle identification of pions, kaons and protons in the momentum range 2-20 GeV/c over a 9.5 m flight path. A detector module, comprising a 10 mm thick quartz plate, provides a source of Cherenkov photons which propagate via total internal reflection to one end of the plate. Here, the photons are focused onto an array of custom-designed Micro-Channel Plate Photo-Multiplier Tubes (MCP-PMTs) which measure their positions and arrival times. The target time resolution per photon is 70 ps which, for 30 detected photons per charged particle, results in a 10-15 ps time-of-flight resolution. A 1.25 m length TORCH prototype module employing two MCP-PMTs has been developed, and tested at the CERN PS using a charged hadron beam of 8 GeV/c momentum. The construction of the module, the properties of the MCP-PMTs and the readout electronics are described. Measurements of the collected photon yields and single-photon time resolutions have been performed as a function of particle entry points on the plate and compared to expectations. These studies show that the performance of the TORCH prototype approaches the design goals for the full-scale detector.

TORCH is a large-area and high-precision time-of-flight detector, designed to provide charged particle identification over a 2-20 GeV/c momentum range. The TORCH detector comprises a 10 mm thick quartz radiator, instrumented with photon detectors, which precisely time and measure the arrival positions of the Cherenkov photons. The photon detectors are micro-channel plate photo-multiplier tubes (MCP-PMTs) comprising a finely segmented anode of 64 x 64 anode pads, electronically ganged into 64 x 8 pixels, over a 53 x 53mm(2) area, an excellent intrinsic time resolution of similar to 30 ps, and a long lifetime of up to greater than or similar to 5 C/cm(2). The current version of the MCP-PMTs used by TORCH have been developed with an industrial partner, Photek Ltd, to satisfy the stringent requirements of the detector. The TORCH R&D programme has successfully demonstrated the detector concept through extensive laboratory and beam tests. A TORCH prototype has been constructed and has yielded encouraging results when exposed to low momentum charged hadrons. Characteristic patterns of Cherenkov photons have been recorded, illustrating the required spatial accuracy and timing resolution of 70 ps per photon. Both laboratory and beam test results are approaching the design goals of the TORCH detector.

The TORCH time-of-flight detector is designed to provide a 15 ps timing resolution for charged particles, resulting in π/K particle identification up to 10 GeV/c momentum over a 10 m flight path. Cherenkov photons, produced in a quartz plate of 10 mm thickness, are focused onto an array of micro-channel plate photomultipliers (MCP-PMTs) which measure the photon arrival times and spatial positions. A half-scale (660 × 1250 × 10 mm3) TORCH demonstrator module has been tested in an 8 GeV/c mixed proton-pion beam at CERN. Customised square MCP-PMTs of active area 53 × 53 mm2 and granularity 64 × 64 pixels have been employed, which have been developed in collaboration with an industrial partner. The single-photon timing performance and photon yields have been measured as a function of beam position in the radiator, giving measurements which are consistent with expectations. The expected performance of TORCH for high luminosity running of the LHCb Upgrade II has been simulated.

M. Kreps0,∗, S. Bhasin, T. Blake, N.H. Brook, M.F. Cicala, T. Conneely , D. Cussans, M.W.U. van Dijk4,1, R. Forty, C. Frei, E.P.M. Gabriel 5 , R. Gao, T. Gershon, T. Gys, T. Hadavizadeh6,2, T.H. Hancock, N. Harnew, T. Jones, J. Milnes , D. Piedigrossi, J. Rademacker, J. Smallwood Department of Physics, University of Warwick, Coventry, UK University of Bath, Claverton Down, Bath, UK H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol, UK Photek Ltd., 26 Castleham Road, St Leonards on Sea, UK CERN, Geneva, Switzerland 5 School of Physics and Astronomy, University of Edinburgh, James Clerk Maxwell Bldg., Edinburgh, UK Denys Wilkinson Laboratory, University of Oxford, Keble Road, Oxford, UK

This erratum corrects measurements of the prompt and secondary (from-b).

The angular distribution of the dimuon system of the decays.

TORCH is a novel time-of-flight detector that has been developed to provide charged-particle identification between 2 and 10 GeV/c momentum. TORCH combines arrival times from multiple Cherenkov photons produced within a 10 mm-thick quartz radiator plate, to achieve a 15 ps time-of-flight resolution per incident particle. A customised Micro-Channel Plate photomultiplier tube (MCP-PMT) and associated readout system utilises an innovative charge-sharing technique between adjacent pixels to obtain the necessary 70 ps time resolution of each Cherenkov photon. A five-year R&D programme has been undertaken, culminating in the construction of a small-scale prototype TORCH module. In testbeams at CERN, this prototype operated successfully with customised electronics and readout system. A full analysis chain has been developed to reconstruct the data and to calibrate the detector. Results are compared to those using a commercial Planacon MCP-PMT, and single photon resolutions approaching 80 ps have been achieved. The photon counting efficiency was found to be in reasonable agreement with a GEANT4 Monte Carlo simulation of the detector. The small-scale demonstrator is a precursor to a full-scale TORCH module (with a radiator plate of 660×1250×10mm3), which is currently under construction.

C. Baesso, M. Cruz Torres, C. Gobel, J. Molina Rodriguez are associated to Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil Y. Xie, J. Yu are associated to Center for High Energy Physics, Tsinghua University, Beijing, China D. A. Milanes, I. A. Monroy, J. A. Rodriguez Lopez are associated to LPNHE, Universite Pierre et Marie Curie, Universite Paris Diderot, CNRS/IN2P3, Paris, France O. Grunberg, M. Hes, C. Vos, R. Waldi are associated to Physikalisches Institut, Ruprecht-Karls-Universitat Heidelberg, Heidelberg, Germany T. Likhomanenko, A. Malinin, V. Shevchenko, A. Ustyuzhanin are associated to Institute of Theoretical and Experimental Physics (ITEP), Moscow, Russia D. Derkach, E. Khairullin, T. Likhomanenko, A. Ustyuzhanin are associated to Institute of Theoretical and Experimental Physics (ITEP), Moscow, Russia F. Martinez Vidal, A. Oyanguren, P. Ruiz Valls, C. Sanchez Mayordomo are associated to Universitat de Barcelona, Barcelona, Spain C. J. G. Onderwater is associated to Nikhef National Institute for Subatomic Physics, Amsterdam, The Netherlands Deceased (T. M. Karbach)

Within the TORCH (Time Of internally Reflected CHerenkov light) R&D project, a small-scale TORCH prototype module is currently under study. Circular-shaped micro-channel plate photon detectors with finely segmented square anodes (32 x 32 channels) have been produced for TORCH requirements in industrial partnership. A new generation of custom multi-channel electronics based on the 32-channel NINO and HPTDC ASICs has been developed. The performance of the photon detector coupled to these customized electronics has been assessed in the laboratory and is reported on. A time resolution of 80 ps and a spatial resolution of 0.03mm have been measured. Finally, tests of the TORCH prototype module illuminated with laser light and in a charged particle beam will be highlighted.

The first study is presented of CP violation with an amplitude analysis of the Dalitz plot of $B^0 D K^+ pi^-$ decays, with $D K^+ pi^-$, $K^+ K^-$ and $pi^+ pi^-$. The analysis is based on a data sample corresponding to $3.0,{rm fb}^{-1}$ of $pp$ collisions collected with the LHCb detector. No significant CP violation effect is seen, and constraints are placed on the angle $gamma$ of the unitarity triangle formed from elements of the Cabibbo-Kobayashi-Maskawa quark mixing matrix. Hadronic parameters associated with the $B^0 D K^*(892)^0$ decay are determined for the first time. These measurements can be used to improve the sensitivity to $gamma$ of existing and future studies of the $B^0 D K^*(892)^0$ decay.

Amplitude models are applied to studies of resonance structure in ${D}^{0}\ensuremath{\rightarrow}{K}_{S}^{0}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$ and ${D}^{0}\ensuremath{\rightarrow}{K}_{S}^{0}{K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ decays using $pp$ collision data corresponding to an integrated luminosity of $3.0\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ collected by the LHCb experiment. Relative magnitude and phase information is determined, and coherence factors and related observables are computed for both the whole phase space and a restricted region of $100\text{ }\text{ }\mathrm{MeV}/{c}^{2}$ around the ${K}^{*}(892{)}^{\ifmmode\pm\else\textpm\fi{}}$ resonance. Two formulations for the $K\ensuremath{\pi}\text{ }S$-wave are used, both of which give a good description of the data. The ratio of branching fractions $\mathcal{B}({D}^{0}\ensuremath{\rightarrow}{K}_{S}^{0}{K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})/\mathcal{B}({D}^{0}\ensuremath{\rightarrow}{K}_{S}^{0}{K}^{\ensuremath{-}}{\mathrm{\ensuremath{\pi}}}^{+})$ is measured to be $0.655\ifmmode\pm\else\textpm\fi{}0.004(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.006(\mathrm{syst})$ over the full phase space and $0.370\ifmmode\pm\else\textpm\fi{}0.003(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.012(\mathrm{syst})$ in the restricted region. A search for $CP$ violation is performed using the amplitude models and no significant effect is found. Predictions from SU(3) flavor symmetry for ${K}^{*}(892)K$ amplitudes of different charges are compared with the amplitude model results.

Citation Aaij, R., C. Abellan Beteta, B. Adeva, M. Adinolfi, A. Affolder, Z. Ajaltouni, S. Akar, et al. “Measurement of the Difference of TimeIntegrated CP Asymmetries in D[superscript 0] K[superscript ]K[superscript +] and D[superscript 0] [superscript ][superscript +] Decays.” Physical Review Letters 116, no. 19 (May 9, 2016). © 2016 CERN, for the LHCb Collaboration As Published http://dx.doi.org/10.1103/PhysRevLett.116.191601 Publisher American Physical Society

bstract An angular analysis of the B 0 → K *0 (→ K + π − ) μ + μ − decay is presented. The dataset corresponds to an integrated luminosity of 3.0 fb −1 of pp collision data collected at the LHCb experiment. The complete angular information from the decay is used to determine CP -averaged observables and CP asymmetries, taking account of possible contamination from decays with the K + π − system in an S-wave configuration. The angular observables and their correlations are reported in bins of q 2 , the invariant mass squared of the dimuon system. The observables are determined both from an unbinned maximum likelihood fit and by using the principal moments of the angular distribution. In addition, by fitting for q 2 -dependent decay amplitudes in the region 1.1 < q 2 < 6.0 GeV 2 / c 4 , the zero-crossing points of several angular observables are computed. A global fit is performed to the complete set of CP -averaged observables obtained from the maximum likelihood fit. This fit indicates differences with predictions based on the Standard Model at the level of 3.4 standard deviations. These differences could be explained by contributions from physics beyond the Standard Model, or by an unexpectedly large hadronic effect that is not accounted for in the Standard Model predictions.