arXiv subjects

M. Bobrowski

Publications and source records attributed to M. Bobrowski.

3 recordsLinked to original sources

arXiv2013

Implications of LHCb measurements and future prospects

During 2011 the LHCb experiment at CERN collected 1.0 fb-1 of sqrt{s} = 7 TeV pp collisions. Due to the large heavy quark production cross-sections, these data provide unprecedented samples of heavy flavoured hadrons. The first results from LHCb have made a significant impact on the flavour physics landscape and have definitively proved the concept of a dedicated experiment in the forward region at a hadron collider. This document discusses the implications of these first measurements on classes of extensions to the Standard Model, bearing in mind the interplay with the results of searches for on-shell production of new particles at ATLAS and CMS. The physics potential of an upgrade to the LHCb detector, which would allow an order of magnitude more data to be collected, is emphasised.

hep-ex↗

arXiv2010

How large can the SM contribution to CP violation in $D^0-\bar D^0$ mixing be?

We investigate the maximum size of CP violating effects in $D$-mixing within the Standard Model (SM), using Heavy Quark Expansion (HQE) as theoretical working tool. For this purpose we determine the leading HQE contributions and also $α_s$ corrections as well as subleading $1/m_c$ corrections to the absorptive part of the mixing amplitude of neutral $D$ mesons. It turns out that these contributions to $Γ_{12}$ do not vanish in the exact SU$(3)_\mathrm{F}$ limit. Moreover, while the leading HQE terms give a result for $Γ_{12}$ orders of magnitude lower than the current experimental value, we do find a sizeable phase. In the literature it was suggested that higher order terms in the HQE might be much less affected by the severe GIM cancellations of the leading terms; it is even not excluded that these higher order terms can reproduce the experimental value of $y$. If such an enhancement is realized in nature, the phase discovered in the leading HQE terms can have a sizeable effect. Therefore, we think that statements like: {\it "CP violating effects in $D$-mixing of the order of $10^{-3}$ to $10^{-2}$ are an unambigous sign of new physics"}--given our limited knowlegde of the SM prediction--are premature. Finally, we give an example of a new physics model that can enhance the leading HQE terms to $Γ_{12}$ by one to two orders of magnitude.

hep-ph↗

arXiv2009

$D-\bar D$ mixing in the framework of the HQE revisited

We reconsider the leading HQE contributions to the absorptive part of the mixing amplitude of neutral $D$ mesons by taking also $α_s$ corrections and subleading $1/m_c$ corrections into account. We show that these contributions to $Γ_{12}$ do not vanish in the exact SU(3)$_F$ limit and they also can have a large phase. Moreover, we give an example of a new physics model that can enhance these leading HQE terms to $Γ_{12}$, which are orders of magnitude lower than the current experimental expectation, by a factor in the upper double-digit range.

hep-ph↗