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Search for Structure in the Bs0 π± Invariant Mass Spectrum

  • Badalov, Alexey
  • Camboni, Alessandro
  • Garrido Beltrán, Lluís
  • Gascón Fora, David
  • Graciani Díaz, Ricardo
  • Graugés Pous, Eugeni
  • Marin Benito, Carla
  • Picatoste Olloqui, Eduardo
  • Rives Molina, Vicente José
  • LHCb Collaboration
The B 0 s π ± invariant mass distribution is investigated in order to search for possible exotic meson states. The analysis is based on a data sample recorded with the LHCb detector corresponding to 3     fb − 1 of p p collision data at √ s = 7 and 8 TeV. No significant excess is found, and upper limits are set on the production rate of the claimed X ( 5568 ) state within the LHCb acceptance. Upper limits are also set as a function of the mass and width of a possible exotic meson decaying to the B 0 s π ± final state. The same limits also apply to a possible exotic meson decaying through the chain B * 0 s π ± , B * 0 s → B 0 s γ where the photon is excluded from the reconstructed decays.
Proyecto:


Studies of the resonance structure in D0 → KS0 K±π decays

  • Garrido Beltrán, Lluís
  • Gascón Fora, David
  • Graciani Díaz, Ricardo
  • Graugés Pous, Eugeni
  • Marin Benito, Carla
  • Picatoste Olloqui, Eduardo
  • Rives Molina, Vicente José
  • Ruiz, Hugo (Ruiz Pérez)
  • LHCb Collaboration
Amplitude models are applied to studies of resonance structure in D 0 → K 0 S K − π + and D 0 → K 0 S K + π − decays using p p collision data corresponding to an integrated luminosity of 3.0     fb − 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     MeV / c 2 around the K ∗ ( 892 ) ± resonance. Two formulations for the K π   S -wave are used, both of which give a good description of the data. The ratio of branching fractions B ( D 0 → K 0 S K + π − ) / B ( D 0 → K 0 S K − π + ) is measured to be 0.655 ± 0.004 ( stat ) ± 0.006 ( syst ) over the full phase space and 0.370 ± 0.003 ( stat ) ± 0.012 ( syst ) in the restricted region. A search for C P 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.
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Study of Bc+ decays to the K+K-π+ final state and evidence for the decay Bc+ →χc0π+

  • Coquereau, S.
  • Garrido Beltrán, Lluís
  • Gascón Fora, David
  • Graciani Díaz, Ricardo
  • Graugés Pous, Eugeni
  • Marin Benito, Carla
  • Picatoste Olloqui, Eduardo
  • Rives Molina, Vicente José
  • LHCb Collaboration
A study of B + c → K + K − π + decays is performed for the first time using data corresponding to an integrated luminosity of 3.0     fb − 1 collected by the LHCb experiment in p p collisions at center-of-mass energies of 7 and 8 TeV. Evidence for the decay B + c → χ c 0 ( → K + K − ) π + is reported with a significance of 4.0 standard deviations, giving σ ( B + c ) σ ( B + ) × B ( B + c → χ c 0 π + ) = ( 9. 8 + 3.4 − 3.0 ( stat ) ± 0.8 ( syst ) ) × 10 − 6 . Here B denotes a branching fraction while σ ( B + c ) and σ ( B + ) are the production cross sections for B + c and B + mesons. An indication of ¯ b c weak annihilation is found for the region m ( K − π + ) < 1.834     GeV / c 2 , with a significance of 2.4 standard deviations.
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Study of DsJ(*) + mesons decaying to D∗ +KS0 and D*0K+ final states

  • Gascón Fora, David
  • Graciani Díaz, Ricardo
  • Graugés Pous, Eugeni
  • Marin Benito, Carla
  • Picatoste Olloqui, Eduardo
  • Rives Molina, Vicente José
  • LHCb Collaboration
A search is performed for D sJ (*) + mesons in the reactions pp → D ∗ + K S 0 X and pp → D *0 K + X using data collected at centre-of-mass energies of 7 and 8 TeV with the LHCb detector. For the D ∗ + K S 0 final state, the decays D *+ → D 0 π + with D 0 → K − π + and D 0 → K − π + π + π − are used. For D *0 K +, the decay D *0 → D 0 π 0 with D 0 → K − π + is used. A prominent D s1(2536)+ signal is observed in both D ∗ + K S 0 and D *0 K + final states. The resonances D s1 * (2700)+ and D s3 * (2860)+ are also observed, yielding information on their properties, including spin-parity assignments. The decay D s2 * (2573)+ → D ∗ + K S 0 is observed for the first time, at a significance of 6.9 σ, and its branching fraction relative to the D s2 * (2573)+ → D + K S 0 decay mode is measured.
Proyecto:


PACIFIC: the readout ASIC for the SciFi Tracker of the upgraded LHCb detector

  • Mazorra, José
  • Chanal, Herve
  • Comerma, Albert
  • Gascón Fora, David
  • Gomez, Sergio
  • Han, X.
  • Pillet, Nicolas
  • Vandaele, R.
  • LHCb Collaboration
The LHCb detector will be upgraded during the Long Shutdown 2 (LS2) of the LHC in order to cope with higher instantaneous luminosities and will switch to a 40 MHz readout rate using a trigger-less software based system. All front-end electronics will be replaced and several sub-detectors must be redesigned to cope with the higher detector occupancy and radiation damage. The current tracking detectors downstream of the LHCb dipole magnet will be replaced by the Scintillating Fibre (SciFi) Tracker. The SciFi Tracker will use scintillating fibres read out by Silicon Photomultipliers (SiPMs). State-of-the-art multi-channel SiPM arrays are being developed and a custom ASIC, called the low-Power ASIC for the sCIntillating FIbres traCker (PACIFIC), will be used to digitise the signals from the SiPMs. This article presents an overview of the R&D for the PACIFIC. It is a 64-channel ASIC implemented in 130 nm CMOS technology, aiming at a radiation tolerant design with a power consumption below 10 mW per channel. It interfaces directly with the SiPM anode through a current mode input, and provides a configurable non-linear 2-bit per channel digital output. The SiPM signal is acquired by a current conveyor and processed with a fast shaper and a gated integrator. The digitization is performed using a three threshold non-linear flash ADC operating at 40 MHz. Simulation and test results show the PACIFIC chip prototypes functioning well.
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Measurement of the ratio of branching fractions ℬ(Bc+→J/ψK+)/ℬ(Bc+→J/ψπ+)

  • Garrido Beltrán, Lluís
  • Gascón Fora, David
  • Graciani Díaz, Ricardo
  • Graugés Pous, Eugeni
  • Marin Benito, Carla
  • Picatoste Olloqui, Eduardo
  • Rives Molina, Vicente José
  • LHCb Collaboration
The ratio of branching fractions RK/π≡B(B+c→J/ψK+)/B(B+c→J/ψπ+) is measured with pp collision data collected by the LHCb experiment at centre-of-mass energies of 7 TeV and 8 TeV, corresponding to an integrated luminosity of 3 fb−1. It is found to be R K/π = 0.079 ± 0.007 ± 0.003, where the first uncertainty is statistical and the second is systematic. This measurement is consistent with the previous LHCb result, while the uncertainties are significantly reduced.
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Observations of Λb0 → ΛK+π− and Λb0 → ΛK+ K− decays and searches for other Λb0 and Ξb0 decays to Λh+ h′− final states

  • Garrido Beltrán, Lluís
  • Gascón Fora, David
  • Graciani Díaz, Ricardo
  • Graugés Pous, Eugeni
  • Marin Benito, Carla
  • Picatoste Olloqui, Eduardo
  • Rives Molina, Vicente José
  • Calvo Gómez, Míriam
  • LHCb Collaboration
A search is performed for the charmless three-body decays of the Λ b 0 and Ξ b 0 baryons to the final states Λh + h′−, where h (′) = π or K. The analysis is based on a data sample, corresponding to an integrated luminosity of 3 fb−1 of pp collisions, collected by the LHCb experiment. The Λ b 0  → ΛK +π− and Λ b 0  → ΛK + K − decays are observed for the first time and their branching fractions and CP asymmetry parameters are measured. Evidence is seen for the Λ b 0  → Λπ+π− decay and limits are set on the branching fractions of Ξ b 0 baryon decays to the Λh + h′− final states.
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Study of ψ(2S) production and cold nuclear matter effects in pPb collisions at √ sNN = 5 TeV

  • Garrido Beltrán, Lluís
  • Gascón Fora, David
  • Graciani Díaz, Ricardo
  • Graugés Pous, Eugeni
  • Marin Benito, Carla
  • Picatoste Olloqui, Eduardo
  • Rives Molina, Vicente José
  • Vilasis-Cardona, Xavier
  • Calvo Gómez, Míriam
  • LHCb Collaboration
The production of ψ(2S) mesons is studied in dimuon final states using proton-lead (pPb) collision data collected by the LHCb detector. The data sample corresponds to an integrated luminosity of 1.6 nb−1. The nucleon-nucleon centre-of-mass energy of the pPb collisions is sNN−−−−√=5 TeV. The measurement is performed using ψ(2S) mesons with transverse momentum less than 14 GeV/c and rapidity y in the ranges 1.5 < y < 4.0 and −5.0 < y < −2.5 in the nucleon-nucleon centre-of-mass system. The forward-backward production ratio and the nuclear modification factor are determined for ψ(2S) mesons. Using the production cross-section results of ψ(2S) and J/ψ mesons from b-hadron decays, the bb¯¯ cross-section in pPb collisions at sNN−−−−√=5 TeV is obtained.
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Measurement of the Bc-meson production fraction and asymmetry in 7 and 13 TeV pp collisions

  • LHCb Collaboration
  • Calvo Gómez, Míriam
  • Camboni, Alessandro
  • Coquereau, Samuel
  • Garrido Beltrán, Lluís
  • Gascón Fora, David
  • Gironella Gironell, P.
  • Graciani Díaz, Ricardo
  • Graugés Pous, Eugeni
  • Manera Escalero, R.
  • Vázquez Gómez, Ricard
  • Vilasis-Cardona, Xavier
The production fraction of the Bc-meson with respect to the sum of B- A nd B0 mesons is measured in both 7 and 13 TeV center-of-mass (c.m.) energy pp collisions produced by the Large Hadron Collider (LHC), using the LHCb detector. The rate, approximately 3.7 per mille, does not change with energy, but shows a transverse momentum dependence. The Bc-Bc+ production asymmetry is also measured and is consistent with zero within the determined statistical and systematic uncertainties of a few percent.
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Amplitude analysis of B± → π±K+K− decays

  • LHCb Collaboration
  • Calvo Gómez, Míriam
  • Camboni, Alessandro
  • Coquereau, Samuel
  • Garrido Beltrán, Lluís
  • Gascón Fora, David
  • Gironella Gironell, Pere
  • Graciani Díaz, Ricardo
  • Graugés Pous, Eugeni
  • Vilasis-Cardona, Xavier
The first amplitude analysis of the B± → π ±K+K− decay is reported based on a data sample corresponding to an integrated luminosity of 3.0 fb−1 of pp collisions recorded in 2011 and 2012 with the LHCb detector. The data are found to be best described by a coherent sum of five resonant structures plus a nonresonant component and a contribution from ππ ↔ KK S-wave rescattering. The dominant contributions in the π ±K∓ and K+K− systems are the nonresonant and the B± → ρ(1450)0π ± amplitudes, respectively, with fit fractions around 30%. For the rescattering contribution, a sizeable fit fraction is observed. This component has the largest CP asymmetry reported to date for a single amplitude of (−66 ± 4 ± 2)%, where the first uncertainty is statistical and the second systematic. No significant CP violation is observed in the other contributions.
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