708 research outputs found
Exploiting the width difference in Bs???
No full textThe photon polarization in B?V? is a sensitive probe of right-handed currents. In the time dependent decay rate of Bs?phi? the coefficients S and H in front of the sin(?mst) and the sinh(??s/2t) terms are sensitive to those right-handed currents. As compared to the Bd system there is a sizable width difference in Bs mesons which leads to the additional measurable observable H. We show with a Monte Carlo simulation that the expected resolution on S and H will be about 0.15 at the LHCb experiment for ??s/?s=0.15 and a data sample of 2 fb?1. We also show that the observable H can be measured from the untagged decay rate of Bs mesons which has considerable experimental advantages as no flavour tag will be required. The resolution on H is inversely proportional to the Bs width difference ??s. These experimental prospects have to be compared with the Standard Model predictions Sphi?=0±0.002 and Hphi?=0.047±0.025+0.015 presented in this Letter. We also give the Standard Model prediction and the experimental sensitivity for the direct CP asymmetry in Bs?phi?
Politisches Vordenken in der Demokratie: Eine Laudatio für Franz Muheim, gehalten am Festakt der Stiftung "Freiheit und Verantwortung", Flüelen, 24. März 2007
No full textSearching for the B0d,s → ∅π+ π- decays
No full textUsing 3 fb-1 of pp collision data collected at √s = 7 and 8 TeV by the LHCb
experiment in the 2011 and 2012 data taking periods, the decays B⁰s → ϕπ+π-
and B⁰d → ϕπ+π- have been studied in the π+π- invariant mass range below
1600 MeV/c². The B⁰s,d → ϕπ+π- branching fractions are determined to be:
B(B⁰s → ϕπ+π-;mππ < 1600) = [3:72 ± 0:18 ± 0:38 ± 0:38] x 10-6
B(B⁰d → ϕπ+π-,mππ < 1600) = [1:75 ± 0:25 ± 0:42 ± 0:14] x 10-7
where the first uncertainty is statistical, the second is systematic, and the third
comes from the normalisation mode B⁰s → ϕϕ. From the π+π- mass distribution
and fits to angular distributions, the resonant decay mode B⁰s → ϕf₀(980) is observed and the branching fraction is measured to be:
B(B⁰s → ϕf₀(980); f₀(980) → π+π-) = [1:23 ± 0:15 ± 0:12 ± 0:12] x 10-6
The fit also requires contributions from B⁰s → ϕf2(1270). A search for a P-wave contribution from B⁰s → ϕρ⁰(770) finds evidence at ~ 4σ but confirmation will require more data. An upper limit of the B⁰s → ϕρ⁰(770) decay branching fraction
at 90% C.L. is measured to be:
B(B⁰s → ϕρ⁰(770)) < 4 x 10-
B and D Spectroscopy at LEP
No full textResults from the four LEP experiments ALEPH, DELPHI, L3, and OPAL on the spectroscopy of B and charmed mesons are presented. The predictions of Heavy Quark Effective Theory (HQET) for the masses and the widths of excited L=1 B mesons are supported by a new measurement from L3. A few B_c candidate eve nts have masses consistent with the recent CDF observation and the predictions. New results on Ddstar production and B -> Ddstar l nu are also presented. The evidence for a Dstarpr meson reported recently by DELPHI is not supported by OPAL and CLEO.Results from the four LEP experiments ALEPH, DELPHI, L3, and OPAL on the spectroscopy of B and charmed mesons are presented. The predictions of Heavy Quark Effective Theory (HQET) for the masses and the widths of excited L=1 B mesons are supported by a new measurement from L3. A few B_c candidate eve nts have masses consistent with the recent CDF observation and the predictions. New results on Ddstar production and B -> Ddstar l nu are also presented. The evidence for a Dstarpr meson reported recently by DELPHI is not supported by OPAL and CLEO.Results from the four LEP experiments ALEPH, DELPHI, L3, and OPAL on the spectroscopy of B and charmed mesons are presented. The predictions of Heavy Quark Effective Theory (HQET) for the masses and the widths of excited L=1 B mesons are supported by a new measurement from L3. A few B_c candidate eve nts have masses consistent with the recent CDF observation and the predictions. New results on Ddstar production and B -> Ddstar l nu are also presented. The evidence for a Dstarpr meson reported recently by DELPHI is not supported by OPAL and CLEO.Results from the four LEP experiments ALEPH, DELPHI, L3, and OPAL on the spectroscopy of B and charmed mesons are presented. The predictions of Heavy Quark Effective Theory (HQET) for the masses and the widths of excited L=1 B mesons are supported by a new measurement from L3. A few B_c candidate eve nts have masses consistent with the recent CDF observation and the predictions. New results on Ddstar production and B -> Ddstar l nu are also presented. The evidence for a Dstarpr meson reported recently by DELPHI is not supported by OPAL and CLEO.Results from the four LEP experiments ALEPH, DELPHI, L3, and OPAL on the spectroscopy of B and charmed mesons are presented. The predictions of Heavy Quark Effective Theory (HQET) for the masses and the widths of excited L=1 B mesons are supported by a new measurement from L3. A few Bc+ candidate events have masses consistent with the recent CDF observation and the predictions. New results on D** production and B→D**lν are also presented. The evidence for a D*′ meson reported recently by DELPHI is not supported by OPAL and CLEO
Multianode Photo Multipliers for Ring Imaging Cherenkov Detectors
No full textThe 64-channel Multianode Photo Multiplier has been evaluated as a possible choice for the photo detectors of the LHCb Ring Imaging Cherenkov detector.The 64-channel Multianode Photo Multiplier has been evaluated as a possible choice for the photo detectors of the LHCb Ring Imaging Cherenkov detector
LHCb Hybrid Photon Detectors and Sensitivity to Flavour Specific Asymmetry in Neutral B-Meson Mixing
No full textThe Large Hadron Collider started operation this year, 2008. LHCb is a precision heavy-flavour experiment at this collider. The precision of LHCb is greatly aided by the LHCb Ring Imaging Cherenkov system for the separation and identification of charged hadrons. This system uses pixel Hybrid Photon Detectors, an innovative new technology for single photon imaging. The simulation and testing of these photon detectors are reported and discussed. The photodetectors were measured to have reached or exceeded the specifications in key areas. In particular, the detector quantum efficiencies far exceed expectations, by a relative 27 %. The precision of LHCb will be used to examine CP-violation and rare decays of B-mesons. A key part of the physics programme will be a measurement of the CP-violating flavour specific asymmetry in neutral B-meson mixing. This asymmetry is expected to bevery small in the Standard Model, of order 10-4, however it is very sensitive to new physics, which can increase the asymmetry dramatically. We present an improved event selection and a novel method to control systematics. This will enable us to make a world-leading measurement of this parameter in one nominal year of data taking (2 fb-1)
LHCb Upgrade Plans
No full textThe LHCb experiment will operate for about five years at a luminosity of 2x10^32 cm^-2 s^-1 and plans are to accumulate a data sample of ~10 fb^-1. Here we present the physics programme and detector design for a future high luminosity phase of the LHCb experiment. An upgraded LHCb experiment would operate at ten times the design luminosity, i.e. at ~2x10^33 cm^-2 s^-1 and aims to collect a data sample of ~100 fb^-1 over five years. This programme would allow the probe of new physics at an unprecedented level. Key measurements include the B^0_s mixing phase phi_s in B^0_s -> J/\psi phi and B^0_s -> phi phi decays with a significant sensitivity to the small Standard Model prediction and a very precise measurement of the CKM angle gamma in tree diagram decays. Initial studies of the modified LHCb trigger and detectors are presented. The upgraded LHCb experiment can run with or without an LHC luminosity upgrade.The LHCb experiment will operate for about five years at a luminosity of 2x10^32 cm^-2 s^-1 and plans are to accumulate a data sample of ~10 fb^-1. Here we present the physics programme and detector design for a future high luminosity phase of the LHCb experiment. An upgraded LHCb experiment would operate at ten times the design luminosity, i.e. at ~2x10^33 cm^-2 s^-1 and aims to collect a data sample of ~100 fb^-1 over five years. This programme would allow the probe of new physics at an unprecedented level. Key measurements include the B^0_s mixing phase phi_s in B^0_s -> J/\psi phi and B^0_s -> phi phi decays with a significant sensitivity to the small Standard Model prediction and a very precise measurement of the CKM angle gamma in tree diagram decays. Initial studies of the modified LHCb trigger and detectors are presented. The upgraded LHCb experiment can run with or without an LHC luminosity upgrade
Status of the LHCb Experiment
No full textWe present the status of the LHCb experiment which will make precision measurements of CP violation in meson decays. The motivation for the experiment and an overview of the detector design are given. The vertex detector, ring imaging Cherenkov counter, calorimeters, and trigger systems are discussed in detail. We also present the expected physics performance for selected modes.We present the status of the LHCb experiment which will make precision measurements of CP violation in meson decays. The motivation for the experiment and an overview of the detector design are given. The vertex detector, ring imaging Cherenkov counter, calorimeters, and trigger systems are discussed in detail. We also present the expected physics performance for selected modes
Measurement of the CP violating phase Φₛ using B⁰ₛ → J/ψK⁺ K⁻ decays at the LHCb experiment
No full textThe LHCb experiment at the Large Hadron Collider (LHC) at CERN is designed to search for indirect evidence of physics beyond the Standard Model (SM) in CP violation and rare decays of beauty and charm hadrons. One of the key measurements is the CP violating phase Φₛ, that arises from the interference between the decay of B⁰ₛ mesons into CP eigenstates directly and via B⁰ₛ- ̅B̅⁰ₛ mixing
In this thesis, the phase Φₛ is measured in the B⁰ₛ → J/ψK⁺ K⁻ decay channel using 1.9 fb−¹ of proton-proton collisions collected at a centre-of-mass energy of √s = 13 TeV. Other parameters that are measured are the average decay width
of the B⁰ₛ meson with respect to that of the B⁰d meson, Γₛ − Γd, the difference in decay widths of the heavy and light mass eigenstates of the B⁰ₛ- ̅B̅⁰ₛ system, ∆Γₛ, and a further parameter that describes the CP violation in interference between
mixing and decay, |λ| .The following results are obtained:
Φₛ = -0:080 ± 0:041 ± 0:006 rad
Γₛ − Γd = 0.0041 ± 0:0024 ± 0:0015 ps⁻¹
∆Γₛ = 0:0764 ± 0:0077 ± 0:0026 ps⁻¹
|λ| = 1:014 ± 0:016 ± 0:006
These are the most precise measurements using a single decay channel. Combining
this analysis with other decay channels measured at the LHCb experiment
that are sensitive to Φₛ yields the most precise measurements to date:
Φₛ = -0.042 ± 0.025 rad
Γₛ = 0.6566 ± 0.025 ps⁻¹
∆Γₛ = 0:0811 ± 0.0048 ps⁻¹
|λ| = 0:993 ± 0:01
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