arXiv subjects

Patrick Koppenburg

Publications and source records attributed to Patrick Koppenburg.

27 records · Page 2Linked to original sources

arXiv2015

Precision physics with heavy-flavoured hadrons

The understanding of flavour dynamics is one of the key aims of elementary particle physics. The last 15 years have witnessed the triumph of the Kobayashi-Maskawa mechanism, which describes all flavour changing transitions of quarks in the Standard Model. This important milestone has been reached owing to a series of experiments, in particular to those operating at the so-called $B$ factories, at the Tevatron, and now at the LHC. We briefly review status and perspectives of flavour physics, highlighting the results where the LHC has given the most significant contributions, notably including the recent observation of the $B_s^0\toμ^+μ^-$ decay

hep-ex↗

arXiv2015

CP violation and CKM studies (and first LHCb Run II results)

The LHC is the new b-hadron factory and will be dominating flavour physics until the start of Belle II, and beyond in many decay modes. While the $B$ factories and Tevatron experiments are still analysing their data, ATLAS, CMS and LHCb are producing interesting new results in CP violation and rare decays, that set strong constraints on models beyond that SM and exhibit some discrepancies with the SM predictions. The LHCb collaboration used the LHC 50 ns ramp-up period of July 2015 to measure the double-differential $J/ψ$, $J/ψ$-from-$b$-hadron and charm cross-sections at $\sqrt{s} = 13$ TeV. Both measurements were performed directly on triggered candidates using a reduced data format that does not require offline processing.

hep-ex↗

arXiv2014

CKM studies from b physics at hadron machines

In absence of direct signs of new physics at the LHC, flavour physics provides an ideal laboratory to look for deviations from the Standard Model and explore an energy regime beyond the LHC reach. Here, new results in CP violation and rare decays are presented.

hep-ex↗

arXiv2012

Branching Ratio Measurements of $B_s$ Decays

We have just entered an era of precision measurements for $B_s$-decay observables. A characteristic feature of the $B_s$-meson system is $B^0_s$--$\bar B^0_s$ mixing, which exhibits a sizable decay width difference. The latter feature leads to a subtle complication for the extraction of branching ratios of $B_s$ decays from untagged data samples, leading to systematic biases as large as O(10%) that depend on the dynamics of the considered decay. We point out that this effect can only be corrected for using information from a time-dependent analysis and suggest the use of the effective $B_s$ decay lifetime, which can already be extracted from the untagged data sample, for this purpose. We also address several experimental issues that can play a role in the extraction of effective lifetimes at a hadron collider, and advocate the use of the $B_s$ branching ratios, as presented in this note, for consistent comparisons of theoretical calculations and experimental measurements in particle listings.

hep-ph↗

arXiv2012

Probing New Physics via the $B^0_s\to μ^+μ^-$ Effective Lifetime

We have recently seen new upper bounds for $B^0_s\to μ^+μ^-$, a key decay to search for physics beyond the Standard Model. Furthermore a non-vanishing decay width difference $ΔΓ_s$ of the $B_s$ system has been measured. We show that $ΔΓ_s$ affects the extraction of the $B^0_s\to μ^+μ^-$ branching ratio and the resulting constraints on the New Physics parameter space, and give formulae for including this effect. Moreover, we point out that $ΔΓ_s$ provides a new observable, the effective $B^0_s\to μ^+μ^-$ lifetime $τ_{μ^+μ^-}$, which offers a theoretically clean probe for New Physics searches that is complementary to the branching ratio. Should the $B^0_s\to μ^+μ^-$ branching ratio agree with the Standard Model, the measurement of $τ_{μ^+μ^-}$, which appears feasible at upgrades of the LHC experiments, may still reveal large New Physics effects.

hep-ph↗

arXiv2011

Heavy Flavour Results at the LHC

We present a brief overview of the first flavour physics results at the LHC. Cross-section for charm and beauty production have been measured by several experiments and the first competitive results on D and B decays are presented.

hep-ex↗

arXiv2010

Extracting gamma and Penguin Parameters from B^0_s -> J/psi K_S

The B^0_s -> J/psi K_S decay has recently been observed by the CDF collaboration and will be of interest for the LHCb experiment. It is the U-spin partner of the golden B^0_d -> J/psi K_S channel and offers a determination of the angle gamma of the unitarity triangle. Moreover, it allows us to control the hadronic penguin effects in the extraction of the B^0_d-\bar B^0_d mixing phase phi_d through a measurement of CP violation in B^0_d^0 -> J/psi K_S. We discuss the picture emerging for these measurements from an LHCb feasibility study. While LHCb will be able to extract gamma from the CP violation in B^0_d -> J/psi K_S, the main application of this channel will be the determination of hadronic penguin parameters. Such an analysis is actually needed in order to fully exploit LHCb's impressive experimental precision for the determination of phi_d from B^0_d -> J/psi K_S. We give also the target regions for the effective lifetime of B^0_s -> J/psi K_S and its CP-violating observables for improved measurements by CDF and the 2011 data taking at LHCb.

hep-ph↗

arXiv2010

Extracting gamma and Penguin Topologies through CP Violation in B_s^0 -> J/psi K_S

The B_s^0 -> J/psi K_S decay has recently been observed by the CDF collaboration and will be of interest for the LHCb experiment. This channel will offer a new tool to extract the angle gamma of the unitarity triangle and to control doubly Cabibbo-suppressed penguin corrections to the determination of sin(2beta) from the well-known B_d^0 -> J/psi K_S mode with the help of the U-spin symmetry of strong interactions. While any competitive determination of gamma is interesting, the latter aspect is particularly relevant as LHCb will enter a territory of precision which makes the control of doubly Cabibbo-suppressed Standard-Model corrections mandatory. Using the data from CDF and the e^+e^- B factories as a guideline, we explore the sensitivity for gamma and the penguin parameters and point out that the B_s^0-\bar B_s^0 mixing phase phi_s, which is only about -2 deg in the Standard Model but may be enhanced through new physics, is a key parameter for these analyses. We find that the mixing-induced CP violation S(B_s^0 -> J/psi K_S) shows an interesting correlation with sin(phi_s), which serves as a target region for the first measurement of this observable at LHCb.

hep-ph↗

arXiv2003

Electroweak Penguin B Decays at Belle

We summarise the most recent results of the Belle experiment about flavour changing neutral current (FCNC) radiative and (semi-) leptonic B decays. In particular, we report about the first observation of the decays B->K*l+l-, B->phi K gamma, the inclusive B->Xs l+l-$. We also report about searches for B->l+l- decay and for CP asymmetries in B->K*gamma.

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