LHCb

Abstract:

Limits on the cross-section times branching fraction for neutral Higgs bosons, produced in pp collisions at √s = 7 TeV, and decaying to two tau leptons with pseudorapidities between 2.0 and 4.5, are presented. The result is based on a dataset, corresponding to an integrated luminosity of 1.0 fb -1, collected with the LHCb detector. Candidates are identified by reconstructing final states with two muons, a muon and an electron, a muon and a hadron, or an electron and a hadron. A model independent upper limit at the 95% confidence level is set on a neutral Higgs boson cross-section times branching fraction. It varies from 8.6 pb for a Higgs boson mass of 90 GeV to 0.7 pb for a Higgs boson mass of 250 GeV, and is compared to the Standard Model expectation. An upper limit on tan β in the Minimal Supersymmetric Model is set in the mh0max scenario. It ranges from 34 for a CP -odd Higgs boson mass of 90 GeV to 70 for a pseudo-scalar Higgs boson mass of 140 GeV. [Figure not available: see fulltext.] © 2013 Cern for the benefit of the LHCb collaboration.

Abstract:

Low mass on-detector cooling systems are being developed and studied by the Detector Technology group (PH-DT) in the CERN Physics Department in close collaboration with LHC and non-LHC experiments. Two approaches are currently being investigated. The first approach, for barrel configurations, consists in integrating the cooling apparatus in light mechanical structures supporting the detectors. In this case, the thermal management can be achieved either with light cooling pipes and thin plates or with a network of microchannels embedded in thin strips of silicon or polyimide. Both configurations are being investigated in the context of the 2018 upgrade program of the ALICE Inner Tracking System (ITS). Moreover, it is also possible to use a silicon microchannel cooling device itself as structural support for the detectors and electronics. Such a configuration has been adopted by the NA62 collaboration for their GigaTracKer (GTK) as well as by the LHCb collaboration for the 2018 major upgrade of the Vertex Locator (VeLo).

Abstract:

The branching fraction of the rare decay B 0 → K *0 e + e - in the dilepton mass region from 30 to 1000 MeV/c 2 has been measured by the LHCb experiment, using pp collision data, corresponding to an integrated luminosity of 1.0 fb-1, at a centre-of-mass energy of 7 TeV. The decay mode B 0 → J/ψ (e + e -)K *0 is utilized as a normalization channel. The branching fraction B(B 0 → K *0 e + e -) is measured to be B(B 0 → K *0 e + e -)30-1000 MeV/c2=(3.1+0.9-0.80.2-0.3 ± 0.2) × 10 -7 where the first error is statistical, the second is systematic, and the third comes from the uncertainties on the B 0 → J/ψ K *0 and J/ψ → e + e - branching fractions. [Figure not available: see fulltext.] © 2013 Cern for the benefit of the LHCb collaboration.

Abstract:

A combination of three LHCb measurements of the CKM angle γ is presented. The decays B±→DK± and B±→Dπ± are used, where D denotes an admixture of D0 and D-0 mesons, decaying into K+K-, π+π-, K±π∓, K±π∓π±π∓, KS0π+π-, or KS0K+K- final states. All measurements use a dataset corresponding to 1.0 fb-1 of integrated luminosity. Combining results from B±→DK± decays alone a best-fit value of γ=72.0° is found, and confidence intervals are setγ∈[56.4,86.7]°at 68% CL,γ∈[42.6,99.6]°at 95% CL. The best-fit value of γ found from a combination of results from B±→Dπ± decays alone, is γ=18.9°, and the confidence intervalsγ∈[7.4,99.2]°∪[167.9,176.4]°at 68% CL are set, without constraint at 95% CL. The combination of results from B±→DK± and B±→Dπ± decays gives a best-fit value of γ=72.6° and the confidence intervalsγ∈[55.4,82.3]°at 68% CL,γ∈[40.2,92.7]°at 95% CL are set. All values are expressed modulo 180°, and are obtained taking into account the effect of D0-D-0 mixing. © 2013 CERN.

Abstract:

Local thermal management of detector electronics through ultra-thin micro-structured silicon cooling plates is a very promising technique for pixel detectors in high energy physics experiments, especially at the LHC where the heavily irradiated sensors must be operated at temperatures below -20 C. It combines a very high thermal efficiency with a very low addition of mass and space, and suppresses all problems of CTE mismatch between the heat source and the heat sink. In addition, the use of CO2 as evaporative coolant liquid brings all the benefits of reliable and stable operation, but the high pressures involved impose additional challenges on the micro channel design and the fluidic connectivity. A series of designs have already been prototyped and tested for LHCb. The challenges, the current status of the measurements and the solutions under development will be described. © 2013 Elsevier B.V.