3,708 research outputs found
LHCb calorimeter from trigger to physics
LHCb is a second generation experiment for CP violation study in B decays. It consists in a 20 meters long single-arm spectrometer to be installed on the future Large Hadron Collider at CERN. For its precision measurement purpose, it combines precise vertex location and particle identification, in addition with a per- formant trigger system able to cope with high flux. This document addresses the use of the calorimeter data for the LHCb trigger and the physics analyses
New Physics in b -> s Transitions and the B_{d,s}^0 -> V_1 V_2 Angular Analysis
We suppose that there is new physics (NP) in b -> s transitions, and examine
its effect on the angular distribution of B_q^0 -> V_1 V_2 (q=d,s), where
V_{1,2} are vector mesons. We find that, in the presence of such NP, the
formulae relating the parameters of the untagged, time-integrated angular
distribution to certain observables (polarization fractions, CP-violating
triple-product asymmetries, CP-conserving interference term) must be modified
from their standard-model forms. This modification is due in part to a nonzero
B^0_q-Bbar^0_q width difference, which is significant only for B^0_s decays. We
re-analyze the B^0_s -> phi phi data to see the effect of these modifications.
As (Delta Gamma_s/2)/Gamma_s ~ 10%, there are O(10%) changes in the derived
observables. These are not large, but may be important given that one is
looking for signals of NP. In addition, if the NP contributes to the b -> s
decay, the measurement of the untagged time-dependent angular distribution
provides enough information to extract all the NP parameters.Comment: 29 pages, 6 figure
Postural control and cognitive decline in older adults: Position versus velocity implicit motor strategy
The present study explored the impact of cognitive decline on postural control strategies in older adults with and without cognitive decline from mild cognitive impairment (MCI) to mild-to-moderate Alzheimer disease (MMAD). We hypothesized that the cognitive decline affected the postural control leading to higher bounding limits of COP velocity dynamics. Based on a cross-sectional design, 175 non-faller older adults were recruited in Angers University Hospital, France, including 50 cognitively healthy individuals [CHI] (mean age 76.42 +/- 4.84 years; 30% women), 64 age-and body mass index-matched participants with MCI (mean age 77.51 +/- 6.32 years; 39% women), and 61 age- and body mass index-matched participants with MMAD (mean age 78.44 +/- 3.97 years; 62% women). For all data collection of postural sway, the participants were asked to maintain quiet stance on force platform. The postural test consisted of two trials of quiet stance, with eyes open and with eyes closed. The COP parameters were mean and standard deviation (SD) of position, velocity and average absolute maximal velocity (AAMV) in anteroposterior and medio-lateral directions. Overall, the analysis concerning all COP parameters revealed a significant main effect of cognitive status on velocity-based variables, with post hoc comparisons evidencing that SD velocity and AAMV increased with cognitive impairment. The current findings suggest an active control (or corrective process) of COP velocity dynamics for CHI, whereas MCI and MMAD are affected by COP movements. (C) 2013 Elsevier B.V. All rights reserved
Implications of CP violating 2HDM in B physics
The charged fermion mass matrices are invariant under symmetry
linked to the fermion number transformation. Under the condition that the
definition of this symmetry in arbitrary weak basis does not depend upon Higgs
parameters such as ratio of vacuum expectation values, a class of two Higgs
doublet models (2HDM) can be identified in which tree level flavor changing
neutral currents normally present in 2HDM are absent. However unlike the type I
or type II Higgs doublet models, the charged Higgs couplings in these models
contain additional flavor dependent CP violating phases. These phases can
account for the recent hints of the beyond standard model CP violation in the
and mixing. In particular, there is a range of parameters in which
new phases do not contribute to the meson CP violation but give identical
new physics phases in the and meson mixing.Comment: 7 pages, 1 figure, Talk given by Bhavik P. Kodrani at 16th
International Symposium on Particles, Strings and Cosmology, July 19th -
23rd, 2010, Valencia, Spai
Quantifying the modern recharge of the "fossil" Sahara aquifers
The North-Western Sahara Aquifer System (NWSAS), one of the world's largest groundwater systems, shows an overall piezometric decline associated with increasing withdrawals. Estimating the recharge rate in such a semiarid system is challenging but crucial for sustainable water development. In this paper, the recharge of the NWSAS is estimated using a regional water budget based on GRACE terrestrial water storage monthly records, soil moisture from the GLDAS (a land data system that assimilates hydrological information), and groundwater pumping rates. A cumulated natural recharge rate of 1.40 +/- 0.90 km(3) yr(-1) is estimated for the two main aquifers. Our results suggest a renewal rate of about 40% which partly contradicts the premise that recharge in this area should be very low or even null. Aquifer depletion inferred from our analysis is consistent with observed piezometric head decline in the two main aquifers in the region. Annual recharge variations were also estimated and vary between 0 and 4.40 km(3) yr(-1) for the period 2003-2010. These values correspond to a recharge between 0 and 6.75 mm yr(-1) on the 650,000 km(2) of outcropping areas of the aquifers, which is consistent with the expected weak and sporadic recharge in this semiarid environment. These variations are also in line with annual rainfall variation with a lag time of about 1 year
Predictions of selected flavour observables within the Standard Model
This letter gathers a selection of Standard Model predictions issued from the
metrology of the CKM parameters performed by the CKMfitter group. The selection
includes purely leptonic decays of neutral and charged B, D and K mesons. In
the light of the expected measurements from the LHCb experiment, a special
attention is given to the radiative decay modes of B mesons as well as to the
B-meson mixing observables, in particular the semileptonic charge asymmetries
a^d,s_SL which have been recently investigated by the D0 experiment at
Tevatron. Constraints arising from rare kaon decays are addressed, in light of
both current results and expected performances of future rare kaon experiments.
All results have been obtained with the CKMfitter analysis package, featuring
the frequentist statistical approach and using Rfit to handle theoretical
uncertainties.Comment: 8 pages, 1 figure, 2 tables. Typos corrected and discussion of
agreement between SM and data update
Level 0 trigger decision unit for the LHCb experiment
The Level-0 Decision Unit (L0DU) is the central part of the first trigger level of the LHCb detector. The L0DU receives information from the Calorimeter, Muon and Pile-Up sub-triggers, with fixed latencies, at 40 MHz via 24 high speed optical fiber links running at 1.6 Gb/s. The L0DU performs simple physics algorithm to compute the decision in order to reduce the data flow down to 1 MHz for the next trigger level and a L0Block is constructed. The processing is implemented in FPGA using a 40 MHz synchronous pipelined architecture. The algorithm can be easily configured with the Experiment Control System (ECS) without FPGA reprogramming. The L0DU is a 16 layer custom board
Moduli spaces of reflexive sheaves of rank 2
Let \sF be a coherent rank 2 sheaf on a scheme Y \subset \proj{n} of
dimension at least two. In this paper we study the relationship between the
functor which deforms a pair (\sF,\sigma), \sigma \in H^0(\sF), and the functor
which deforms the corresponding pair (X,\xi) given as in the Serre
correspondence. We prove that the scheme structure of e.g. the moduli scheme
M_Y(P) of stable sheaves on a threefold Y at (\sF), and the scheme structure at
(X) of the Hilbert scheme of curves on Y are closely related. Using this
relationship we get criteria for the dimension and smoothness of M_Y(P) at
(\sF), without assuming Ext^2(\sF,\sF) = 0. For reflexive sheaves on Y =
\proj{3} whose deficiency module M = H_{*}^1(\sF) satisfies Ext^2(M,M) = 0 in
degree zero (e.g. of diameter at most 2), we get necessary and sufficient
conditions of unobstructedness which coincide in the diameter one case. The
conditions are further equivalent to the vanishing of certain graded Betti
numbers of the free graded minimal resolution of H_{*}^0(\sF). It follows that
every irreducible component of M_{\proj{3}}(P) containing a reflexive sheaf of
diameter one is reduced (generically smooth). We also determine a good lower
bound for the dimension of any component of M_{\proj{3}}(P) which contains a
reflexive stable sheaf with "small" deficiency module M.Comment: 19 page
Deformations of modules of maximal grade and the Hilbert scheme at determinantal schemes
Let R be a polynomial ring and M a finitely generated graded R-module of
maximal grade (which means that the ideal I_t(\cA) generated by the maximal
minors of a homogeneous presentation matrix, \cA, of M has maximal codimension
in R). Suppose X:=Proj(R/I_t(\cA)) is smooth in a sufficiently large open
subset and dim X > 0. Then we prove that the local graded deformation functor
of M is isomorphic to the local Hilbert (scheme) functor at X \subset Proj(R)
under a week assumption which holds if dim X > 1. Under this assumptions we get
that the Hilbert scheme is smooth at (X), and we give an explicit formula for
the dimension of its local ring. As a corollary we prove a conjecture of R. M.
Mir\'o-Roig and the author that the closure of the locus of standard
determinantal schemes with fixed degrees of the entries in a presentation
matrix is a generically smooth component V of the Hilbert scheme. Also their
conjecture on the dimension of V is proved for dim X > 0. The cohomology
H^i_{*}({\cN}_X) of the normal sheaf of X in Proj(R) is shown to vanish for 0 <
i < dim X-1. Finally the mentioned results, slightly adapted, remain true
replacing R by any Cohen-Macaulay quotient of a polynomial ring.Comment: 24 page
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