73,438 research outputs found
Prospects for gamma measurements at LHCb
LHCb is the dedicated B physics experiment at the LHC and is due to start
data taking later this year. Its goal is to search for new physics in very rare
processes and make precision measurements of CP violation in B decays. The CKM
angle gamma plays an important role in flavour physics in the Standard Model.
LHCb will exploit the large variety of B hadrons produced by the 14 TeV pp
collisions, performing gamma measurements to the precision of a few degrees.
Here, we will present a summary of the expected gamma sensitivities LHCb will
reach during its first years of data taking, with contributions from several
strategies in both tree and loop processes.Comment: 4 pages, 3 figures. For proceedings of 2009 Lake Louise Winter
Institute, Alberta, Canad
Generalized Stability of Heisenberg Coefficients
Stembridge introduced the notion of stability for Kronecker triples which
generalize Murnaghan's classical stability result for Kronecker coefficients.
Sam and Snowden proved a conjecture of Stembridge concerning stable Kronecker
triple, and they also showed an analogous result for Littlewood--Richardson
coefficients. Heisenberg coefficients are Schur structure constants of the
Heisenberg product which generalize both Littlewood--Richardson coefficients
and Kronecker coefficients. We show that any stable triple for Kronecker
coefficients or Littlewood--Richardson coefficients also stabilizes Heisenberg
coefficients, and we classify the triples stabilizing Heisenberg coefficients.
We also follow Vallejo's idea of using matrix additivity to generate Heisenberg
stable triples.Comment: 13 page
A two step model for linear prediction, with connections to PLS
In the thesis, we consider prediction of a univariate response variable, especially when the explanatory variables are almost collinear. A two step approach has been proposed. The first step is to summarize the information in the explanatory variables via a bilinear model with a Krylov structured design matrix. The second step is the prediction step where a conditional predictor is applied. The two step approach gives us a new insight in partial least squares regression (PLS). Explicit maximum likelihood estimators of the variances and mean for the explanatory variables are derived. It is shown that the mean square error of the predictor in the two step model is always smaller than the one in PLS. Moreover, the two step model has been extended to handle grouped data. A real data set is analyzed to illustrate the performance of the two step approach and to compare it with other regularized methods
Noise threshold and resource cost of fault-tolerant quantum computing with Majorana fermions in hybrid systems
Fault-tolerant quantum computing in systems composed of both Majorana
fermions and topologically unprotected quantum systems, e.g. superconducting
circuits or quantum dots, is studied in this paper. Errors caused by
topologically unprotected quantum systems need to be corrected with error
correction schemes, for instance, the surface code. We find that the
error-correction performance of such a hybrid topological quantum computer is
not superior to a normal quantum computer unless the topological charge of
Majorana fermions is insusceptible to noise. If errors changing the topological
charge are rare, the fault-tolerance threshold is much higher than the
threshold of a normal quantum computer, and a surface-code logical qubit could
be encoded in only tens of topological qubits instead of about a thousand
normal qubits.Comment: 15 pages, 11 figure
Optimizing Higgs factories by modifying the recoil mass
It is difficult to measure the -fusion Higgs production process () at a lepton collider with a center of mass energy of
240-250 GeV due to its small rate and the large background from the
Higgsstrahlung process with an invisible (). We construct a modified recoil mass variable, , defined using only the 3-momentum of the reconstructed Higgs
particle, and show that it can better separate the -fusion and
Higgsstrahlung events than the original recoil mass variable .
Consequently, the variable can be used to improve the
overall precisions of the extracted Higgs couplings, in both the conventional
framework and the effective-field-theory framework. We also explore the
application of the variable in the inclusive cross section
measurements of the Higgsstrahlung process, while a quantitive analysis is left
for future studies.Comment: 25 pages, 8 figure
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