27 research outputs found
Performance of the LHCb outer tracker
The LHCb Outer Tracker is a gaseous detector covering an area of 5 Ă 6 m2 with 12 double layers of straw tubes. The detector with its services are described together with the commissioning and calibration procedures. Based on data of the first LHC running period from 2010 to 2012, the performance of the readout electronics and the single hit resolution and efficiency are presented. The efficiency to detect a hit in the central half of the straw is estimated to be 99.2%, and the position resolution is determined to be approximately 200 ÎŒm. The Outer Tracker received a dose in the hottest region corresponding to 0.12 C/cm, and no signs of gain deterioration or other ageing effects are observed
Search for long-lived particles decaying to jet pairs
A search is presented for long-lived particles with a mass between 25 and 50
GeV and a lifetime between 1 and 200 ps in a sample of proton-proton
collisions at a centre-of-mass energy of TeV, corresponding to an
integrated luminosity of 0.62 fb, collected by the LHCb detector. The
particles are assumed to be pair-produced by the decay of a Standard Model-like
Higgs boson. The experimental signature of the long-lived particle is a
displaced vertex with two associated jets. No excess above the background is
observed and limits are set on the production cross-section as a function of
the long-lived particle mass and lifetime
Search for long-lived heavy charged particles using a ring imaging Cherenkov technique at LHCb
A search is performed for heavy long-lived charged particles using 3.0
fb of pp collisions collected at = 7 and 8 TeV with the LHCb
detector. The search is mainly based on the response of the ring imaging
Cherenkovdetectors to distinguish the heavy, slow-moving particles from muons.
No evidence is found for the production of such long-lived states. The results
are expressed as limits on the Drell-Yan production of pairs of long-lived
particles, with both particles in the LHCb pseudorapidity acceptance, . The mass-dependent cross-section upper limits are in the range 2-4
fb (at 95\% CL) for masses between 124 and 309 GeV/c
Measurement of the lifetime of the meson using the decay mode
The difference in total widths between the and mesons is
measured using 3.0fb of data collected by the LHCb experiment in 7 and 8
TeV centre-of-mass energy proton-proton collisions at the LHC. Through the
study of the time evolution of and
decays, the width difference is measured to be
where the first uncertainty is statistical and the second
systematic. The known lifetime of the meson is used to convert this to a
precise measurement of the lifetime,
where the first uncertainty is
statistical and the second systematic.Comment: 19 pagers, 3 figure
Study of the rare B-s(0) and B-0 decays into the pi(+) pi(-) mu(+) mu(-) final state
A search for the rare decays and is performed in a data set corresponding to an integrated
luminosity of 3.0 fb collected by the LHCb detector in proton-proton
collisions at centre-of-mass energies of 7 and 8 TeV. Decay candidates with
pion pairs that have invariant mass in the range 0.5-1.3 GeV/ and with
muon pairs that do not originate from a resonance are considered. The first
observation of the decay and the first
evidence of the decay are obtained and the
branching fractions, restricted to the dipion-mass range considered, are
measured to be and
, where the third
uncertainty is due to the branching fraction of the decay , used as a normalisation.Comment: 21 pages, 3 figures, 2 Table
Measurement of the CP-violating phase in decays and limits on penguin effects
Time-dependent CP violation is measured in the channel for each resonant final state using data
collected with an integrated luminosity of 3.0 fb in collisions
using the LHCb detector. The final state with the largest rate,
, is used to measure the CP-violating angle to be . This result can be used to
limit the size of penguin amplitude contributions to CP violation measurements
in, for example, decays. Assuming approximate
SU(3) flavour symmetry and neglecting higher order diagrams, the shift in the
CP-violating phase is limited to be within the interval
[, +] at 95% confidence level. Changes to the limit
due to SU(3) symmetry breaking effects are also discussed.Comment: 18 pages, 6 figures; v2-updated from reviewers comments and added a
figur
Cu K-edge EXAFS characterisation of copper(I) arenethiolate complexes in both the solid and liquid state: detection of Cu??Cu Coordination
Herein we describe a structural characterisation with EXAFS of
copper(I) arenethiolate complexes in both the solid and liquid state. Previously noted difficulties in the detection of the Cu??Cu interaction have been attributed to anti-phase behaviour of different Cu??Cu neighbour contributions. A data analysis procedure solely based on EXAFS parameters is presented which resolves these problems. A careful analysis of the individual coordination shells and the use of different kweightings during the data analysis are shown to be an absolute necessity to obtain reliable results. During R-space fitting, the difference file technique is used to separate, examine and compare the individual contributions. Using this technique their statistical significance and correctness can be determined. Anti-phase behaviour can be detected and accounted for in this way. An additional mixed organocopper aggregate [Cu4(SAr)2(Mes)2] with different Cu sites is analysed, which proves the value of the analysis procedure described above. Moreover, this newly developed EXAFS data analysis procedure is applicable to any other EXAFS spectrum obtained. The structural analysis of these organocopper complexes with EXAFS provides information about their actual structure and dynamic behaviour
in solution. The technique can now be used to obtain insights into the reactivity of these complexes and the way in which
they form catalytic reaction intermediates
Diastereoselective self-assembly of chiral diamine-chelated aryllithiums to dimeric aggregates
Aryllithium compounds [LiC6H4(CH2N(Et) CH2CH2NEt2)-2]2(2b), [LiC6H4(CH(Me)N(Me)CH2-CH2NMe2-(R))-2]2((R)-3b), and [LiC6H4(CH(Me)N(Me)CH2CH2NMe2-(rac))-2]2((rac)-3b) were synthesized and characterized in the solid state and in solution. X-ray crystallographic studies of 2b and (R)-3b and molecular weight determinations of 2b, (R)-3b, and (rac)-3b by cryoscopy in benzene showed that, both in the solid state and in apolar, noncoordinating solvents such as benzene, these compounds exist as discrete dimeric aggregates. For (R)-3b and (rac)-3b the aggregation process of two monomeric aryllithium units to one dimer is highly diastereoselective