arXiv subjects

Thomas Kuhr

Publications and source records attributed to Thomas Kuhr.

33 records · Page 2Linked to original sources

arXiv2019

Implementation of GENFIT2 as an experiment independent track-fitting framework

The GENFIT toolkit, initially developed at the Technische Universitaet Muenchen, has been extended and modified to be more general and user-friendly. The new GENFIT, called GENFIT2, provides track representation, track-fitting algorithms and graphic visualization of tracks and detectors, and it can be used for any experiment that determines parameters of charged particle trajectories from spacial coordinate measurements. Based on general Kalman filter routines, it can perform extrapolations of track parameters and covariance matrices. It also provides interfaces to Millepede II for alignment purposes, and RAVE for the vertex finder. Results of an implementation of GENFIT2 in basf2 and PandaRoot software frameworks are presented here.

physics.data-an↗

arXiv2018

B2BII - Data conversion from Belle to Belle II

We describe the conversion of simulated and recorded data by the Belle experiment to the Belle~II format with the software package \texttt{b2bii}. It is part of the Belle~II Analysis Software Framework. This allows the validation of the analysis software and the improvement of analyses based on the recorded Belle dataset using newly developed analysis tools.

hep-ex↗

arXiv2018

HEP Software Foundation Community White Paper Working Group - Software Development, Deployment and Validation

The High Energy Phyiscs community has developed and needs to maintain many tens of millions of lines of code and to integrate effectively the work of thousands of developers across large collaborations. Software needs to be built, validated, and deployed across hundreds of sites. Software also has a lifetime of many years, frequently beyond that of the original developer, it must be developed with sustainability in mind. Adequate recognition of software development as a critical task in the HEP community needs to be fostered and an appropriate publication and citation strategy needs to be developed. As part of the HEP Softare Foundation's Community White Paper process a working group on Software Development, Deployment and Validation was formed to examine all of these issues, identify best practice and to formulare recommendations for the next decade. Its report is presented here.

physics.comp-ph↗

arXiv2017

A Challenge to Lepton Universality in B Meson Decays

One of the key assumptions of the Standard Model of fundamental particles is that the interactions of the charged leptons, namely electrons, muons, and taus, differ only because of their different masses. While precision tests comparing processes involving electrons and muons have not revealed any significant violation of this assumption, recent studies involving the higher-mass tau lepton have resulted in observations that challenge lepton universality at the level of four standard deviations. A confirmation of these results would point to new particles or interactions, and could have profound implications for our understanding of particle physics.

hep-ex↗

arXiv2014

An automated framework for hierarchical reconstruction of B mesons at the Belle II experiment

We present a software framework for Belle II that reconstructs B mesons in many decay modes with minimal user intervention. It does so by reconstructing particles in user-supplied decay channels, and then in turn using these reconstructed particles in higher-level decays. This hierarchical reconstruction allows one to cover a relatively high fraction of all B decays by specifying a limited number of particle decays. Multivariate classification methods are used to achieve a high signal-to-background ratio in each individual channel. The entire reconstruction, including the application of pre-cuts and classifier trainings, is automated to a high degree and will allow users to retrain to account for analysis-specific signal-side selections.

hep-ex↗

arXiv2011

Updated Search for B(s) -> mu+mu- at CDF

The decay Bs -> mu+mu- is very sensitive to contributions from new physics processes. Thus the Tevatron and LHC experiments are hunting for an observation of a Bs -> mu+mu- signal. In this article the updated search for Bs -> mu+mu- and B0 -> mu+mu- by the CDF experiment is presented. The CDF result was received with great interest because an excess over the background expectation is seen, although of modest statistical significance and still consistent with the prediction of a standard model signal and other experimental results.

hep-ex↗

arXiv2011

A Hierarchical NeuroBayes-based Algorithm for Full Reconstruction of B Mesons at B Factories

We describe a new B-meson full reconstruction algorithm designed for the Belle experiment at the B-factory KEKB, an asymmetric e+e- collider that collected a data sample of 771.6 x 10^6 BBbar pairs during its running time. To maximize the number of reconstructed B decay channels, it utilizes a hierarchical reconstruction procedure and probabilistic calculus instead of classical selection cuts. The multivariate analysis package NeuroBayes was used extensively to hold the balance between highest possible efficiency, robustness and acceptable consumption of CPU time. In total, 1104 exclusive decay channels were reconstructed, employing 71 neural networks altogether. Overall, we correctly reconstruct one B+/- or B0 candidate in 0.28% or 0.18% of the BBbar events, respectively. Compared to the cut-based classical reconstruction algorithm used at the Belle experiment, this is an improvement in efficiency by roughly a factor of 2, depending on the analysis considered. The new framework also features the ability to choose the desired purity or efficiency of the fully reconstructed sample freely. If the same purity as for the classical full reconstruction code is desired ~25%, the efficiency is still larger by nearly a factor of 2. If, on the other hand, the efficiency is chosen at a similar level as the classical full reconstruction, the purity rises from ~25% to nearly 90%.

hep-ex↗

arXiv2011

Heavy Flavor Baryons at the Tevatron

The Tevatron experiments CDF and D0 have filled many empty spots in the spectrum of heavy baryons over the last few years. The most recent results are described in this article: The first direct observation of the Xi_b^0, improved measurements of Sigma_b properties, a new measurement of the Lambda_b -> J/psi Lambda branching ratio, and a high-statistics study of charm baryons.

hep-ex↗

arXiv2011

Bs Physics

While B0 and B+ mesons are well studied, mainly by the B factories, less is known about Bs mesons. Specifically large new physics effects may still be present in the Bs system. This unexplored region is studied by the CDF, D0, and Belle experiments. In this article their recent measurements on the Bs physics sector are presented.

hep-ex↗

arXiv2011

Status of SuperKEKB and Belle II

High precision flavor physics measurements are an essential complement to the direct searches for new physics at the LHC. Such measurements can be performed at an upgraded KEKB accelerator. The status of the SuperKEKB collider and Belle II detector is presented in this article.

hep-ex↗

arXiv2010

Upsilon polarization measurement at CDF

Measurements of production cross sections and polarizations are essential inputs for a theoretical understanding of heavy vector meson production. In this article the CDF measurement of the Y(1S) polarization in the kinematic range |y|<0.6 and 2 < pT [GeV/c] < 40 using a data sample of 2.9/fb is described. Compared to the CDF Run I measurement, with which it agrees, it extends the covered pT range, allowing for a better comparison to predictions in the perturbative regime. The observed trend towards longitudinal polarization at high transverse momentum disagrees with predictions based on non-relativistic QCD.

hep-ex↗

arXiv2009

New Charmonium-like States at B-Factories

Since the discovery of the X(3872) in 2003 the B-factory experiments BaBar and Belle have been driving forces in the spectroscopy of new charmonium-like states. In this article the latest results on the decays X(3872) -> D0 D*0bar and X(3872) -> psi gamma, where psi stands for J/psi or psi(2S), are presented and analyses of Z(4430)+ -> psi pi+ and Z(4050/4250)+ -> chi_c1 pi+ are discussed.

hep-ex↗

arXiv2009

Search for New Physics in the Bs Sector at the Tevatron

While B0 and B+ mesons are well studied at B-factories, large samples of B0s mesons are only available at the Tevatron so far. Since the B0s meson consists of quarks of the second and third generation it provides a complementary probe for searches for new physics effects. Results of the CDF and D0 experiments on the decays B0s -> mu+ mu- and B0s -> mu+ mu- phi as well as on CP violation in B0s mixing and in interference between mixing and decay are presented.

hep-ex↗

arXiv2008

Rare B and Charm Decays at the Tevatron

The measurements of rare decays are highly sensitive to physics beyond the standard model. In this article limits on the branching ratios of the decays B0s -> mu+mu-, D0 -> mu+mu- and D+ -> pi+mu+mu- are presented. Furthermore the first measurement of the branching fraction and CP asymmetry of Lambda_b -> p pi- and Lambda_b -> p K- decays is described. Data samples with an integrated luminosity of up to 2/fb collected at the Tevatron ppbar-collider at sqrt(s)=1.96 TeV were used in these analyses. The results are consistent with the standard model predictions and tighten the constraints on new physics models.

hep-ex↗

arXiv2007

Lifetime Difference and CP Asymmetry in the Bs -> J/psi phi decay

The Bs meson is an interesting particle to study because a sizable mixing induced CP violation in the Bs-Bsbar system would be an indication for physics beyond the Standard Model. In this paper we present a measurement of the lifetime difference DeltaGamma between the Bs mass eigenstates and the CP violating phase in the decay Bs -> J/psi phi. In 1.7 fb^-1 of data collected with the CDF II detector at the Tevatron ppbar collider we measure DeltaGamma = 0.076 +0.059-0.063 (stat.) +- 0.006 (syst.) ps^-1, well consistent with the Standard Model prediction, and a mean Bs lifetime of ctau_s = 456 +-13 (stat.) +- 7 (syst.) m^-6. We find no evidence for CP violation.

hep-ex↗