58 research outputs found
Interpreting CP Asymmetries in B->pi+ pi- Decays
We discuss methods used to interpret the measurements of CP-asymmetry in
B->pi+pi- within the framework of the Standard Model. Interpretations using
various theoretical inputs are given, ranging from the rather general, yet
unpredictive, properties based on strong isospin symmetry to highly predictive
calculations using QCD Factorization. The calculations are performed using the
software package CKMFitter and a frequentist method, Rfit.Comment: Invited talk at the Workshop on the CKM Unitarity Triangle, IPPP
Durham, April 2003 (eConf C0304052). 4 pages LaTeX, 4 eps figure
New developments in event generator tuning techniques
Data analyses in hadron collider physics depend on background simulations
performed by Monte Carlo (MC) event generators. However, calculational
limitations and non-perturbative effects require approximate models with
adjustable parameters. In fact, we need to simultaneously tune many
phenomenological parameters in a high-dimensional parameter-space in order to
make the MC generator predictions fit the data. It is desirable to achieve this
goal without spending too much time or computing resources iterating parameter
settings and comparing the same set of plots over and over again. We present
extensions and improvements to the MC tuning system, Professor, which addresses
the aforementioned problems by constructing a fast analytic model of a MC
generator which can then be easily fitted to data. Using this procedure it is
for the first time possible to get a robust estimate of the uncertainty of
generator tunings. Furthermore, we can use these uncertainty estimates to study
the effect of new (pseudo-) data on the quality of tunings and therefore decide
if a measurement is worthwhile in the prospect of generator tuning. The
potential of the Professor method outside the MC tuning area is presented as
well.Comment: To appear in the proceedings of the 13th International Workshop on
Advanced Computing and Analysis Techniques in Physics Research, ACAT2010,
Jaipur, India, February 22-27, 201
Towards a global fit to extract the B->Xs gamma decay rate and Vub
The total B->Xs gamma decay rate and the CKM-matrix element Vub play an
important role in finding indirect evidence for new physics affecting the
flavor sector of the Standard Model, complementary to direct searches at the
LHC and Tevatron. Their determination from inclusive B-meson decays requires
the precise knowledge of the parton distribution function of the b quark in the
B meson, called the shape function. We implement a new model-independent
framework for the shape function with reliable uncertainties based on an
expansion in a suitable set of basis functions. We present the current status
of a global fit to BaBar and Belle data to extract the shape function and the
B->Xs gamma decay rate.Comment: 5 pages, 9 figure
A model independent determination of the B -> Xs gamma decay rate
The goal of the SIMBA collaboration is to provide a global fit to the
available measurements of inclusive B -> X_s gamma and B -> X_u l nu decays. By
performing a global fit one is able to simultaneously determine the relevant
normalizations, i.e. the total B -> X_s gamma rate and the CKM-matrix element
|Vub|, together with the required hadronic parameters, most importantly the
b-quark mass and the b-quark distribution function in the B-meson, called the
shape function. In this talk, the current status on the model-independent
determination of the shape function and |C7^\incl Vtb Vts*|, which parametrizes
the total B -> Xs gamma rate, from a global fit to the available B -> X_s gamma
measurements from Babar and Belle is presented. In particular, the theoretical
uncertainties originating from variations of the different factorization scales
are evaluated.Comment: Proceedings of CKM 2012, the 7th International Workshop on the CKM
Unitarity Triangle, University of Cincinnati, USA, 28 September - 2 October
201
Alternative glues for the production of ATLAS silicon strip modules for the Phase-II upgrade of the ATLAS Inner Detector
The Phase-II upgrade of the ATLAS detector for the High Luminosity Large
Hadron Collider (HL-LHC) includes the replacement of the current Inner Detector
with an all-silicon tracker consisting of pixel and strip detectors. The
current Phase-II detector layout requires the construction of 20,000 strip
detector modules consisting of sensor, circuit boards and readout chips, which
are connected mechanically using adhesives. The adhesive between readout chips
and circuit board is a silver epoxy glue as was used in the current ATLAS
SemiConductor Tracker (SCT). This glue has several disadvantages, which
motivated the search for an alternative.
This paper presents a study concerning the use of six ultra-violet (UV) cure
glues and a glue pad for use in the assembly of silicon strip detector modules
for the ATLAS upgrade. Trials were carried out to determine the ease of use,
the thermal conduction and shear strength, thermal cycling, radiation hardness,
corrosion resistance and shear strength tests. These investigations led to the
exclusion of three UV cure glues as well as the glue pad.
Three UV cure glues were found to be possible better alternatives. Results
from electrical tests of first prototype modules constructed using these glues
are presented.Comment: 23 pages, to be published in Journal of Instrumentatio
Status of SIMBA
The goal of the SIMBA collaboration is to provide a global fit to the available data in inclusive B -> X_s gamma and B -> X_u l nu decays. By performing a global fit one is able to simultaneously determine the relevant normalizations, i.e. the total B -> X_s gamma rate and the CKM-matrix element |Vub|, together with the required input parameters, most importantly the b-quark mass and the b-quark distribution function in the B-meson, called the shape function. This strategy is analogous to the determination of |Vcb| from global fits to inclusive B -> X_c l nu decays. In this talk, we present preliminary results for the shape function and |C_7^incl Vtb Vts^*|, which parametrizes the total B -> X_s gamma rate, from a global fit to the available B -> X_s gamma measurements from BABAR and Belle
Precision Global Determination of the Decay Rate
We perform the first global fit to inclusive measurements
using a model-independent treatment of the nonperturbative -quark
distribution function, with next-to-next-to-leading logarithmic resummation and
fixed-order contributions. The normalization of the
decay rate, given by , is sensitive to physics beyond the Standard Model (SM). We
determine , in good
agreement with the SM prediction, and the -quark mass .
Our results suggest that the uncertainties in the extracted
rate have been underestimated by up to a factor of two, leaving more room for
beyond-SM contributions.Comment: 21 pages, 8 figure
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