arXiv subjects
Publications and source records attributed to Johannes Albrecht.
This article discusses tests of lepton flavour universality that are carried out with the LHCb experiment. The experimental situation of \btosll and $b \to c \ell ν$ decays is summarised.
A range of flavour physics observables show tensions with their corresponding Standard Model expectations: measurements of leptonic flavour-changing neutral current processes and ratios of semi-leptonic branching fractions involving different generations of leptons show deviations of the order of four standard deviations. If confirmed, either would be an intriguing sign of new physics. In this manuscript, we analyse the current experimental situation of such processes and for the first time estimate the combined impact of the future datasets of the Belle II and LHCb experiments on the present tensions with the Standard Model expectations by performing scans of the new physics contribution to the Wilson coefficients. In addition, the present day and future sensitivity of tree-level CKM parameters, which offer orthogonal tests of the Standard Model, are explored. Three benchmark points in time are chosen for a direct comparison of the estimated sensitivity between the experiments. A high complementarity between the future sensitivity achieved by the Belle II and LHCb experiments is observed due to their relative strengths and weaknesses. We estimate that all of the anomalies considered here will be either confirmed or ruled out by both experiments independently with very high significance by the end of data-taking at Belle II and the LHCb upgrade.
Realizing the physics programs of the planned and upgraded high-energy physics (HEP) experiments over the next 10 years will require the HEP community to address a number of challenges in the area of software and computing. For this reason, the HEP software community has engaged in a planning process over the past two years, with the objective of identifying and prioritizing the research and development required to enable the next generation of HEP detectors to fulfill their full physics potential. The aim is to produce a Community White Paper which will describe the community strategy and a roadmap for software and computing research and development in HEP for the 2020s. The topics of event reconstruction and software triggers were considered by a joint working group and are summarized together in this document.
Realizing the physics programs of the planned and upgraded high-energy physics (HEP) experiments over the next 10 years will require the HEP community to address a number of challenges in the area of software and computing. For this reason, the HEP software community has engaged in a planning process over the past two years, with the objective of identifying and prioritizing the research and development required to enable the next generation of HEP detectors to fulfill their full physics potential. The aim is to produce a Community White Paper which will describe the community strategy and a roadmap for software and computing research and development in HEP for the 2020s. The topics of event reconstruction and software triggers were considered by a joint working group and are summarized together in this document.
The LHCb experiment will operate at a luminosity of $2\times10^{33}$ cm$^{-2}$s$^{-1}$ during LHC Run 3. At this rate the present readout and hardware Level-0 trigger become a limitation, especially for fully hadronic final states. In order to maintain a high signal efficiency the upgraded LHCb detector will deploy two novel concepts: a triggerless readout and a full software trigger.
Rare heavy flavor decays are an ideal place to search for the effects of potential new particles that modify the decay rates or the Lorentz structure of the decay vertices. The LHCb experiment, a dedicated heavy flavour experiment at the LHC at CERN. It has recorded the worlds largest sample of heavy meson and lepton decays. The status of the rare decay analyses with 1\,fb$^{-1}$ of $\sqrt s = 7\,$TeV and 1.1\,fb$^{-1}$ of $\sqrt s = 8\,$TeV of $pp$--collisions collected by the LHCb experiment in 2011 and 2012 is reviewed. The worlds most precise measurements of the angular structure of $B^0\rightarrow K^{*0} μ^+ μ^-$ and $B^+\rightarrow K^{+} μ^+ μ^-$ decays is discussed, as well as the isospin asymmetry measurement in $B\rightarrow K^{(*)} μ^+ μ^-}$ decays. The first evidence for the very rare decay $B^0_s \rightarrow μ^+ μ^-$ is presented together with the most stringent upper exclusion limits on the branching fraction of decays of $B^0$, $D^0$ and $K^0_s$ mesons into two muons. This note finishes with the discussion of searches for lepton number and lepton flavor violating $τ$ decays.
A search for the rare decays $B^0_s\rightarrow μ^+μ^-$ and $B^0\rightarrow μ^+μ^-$ is performed with the LHCb experiment using 1.1\,fb$^{-1}$ of data collected at $\sqrt s=8$\,TeV$ and 1.0\,fb$^{-1}$ of data collected at $\sqrt s=7$\,TeV. An excess of $B^0_s\rightarrow μ^+μ^-$ candidates with respect to the background expectations is observed with a statistical significance of 3.5 standard deviations. A branching fraction of ${\cal BR}(B^0_s\rightarrow μ^+μ^-) =(3.2^{+1.5}_{-1.2}) \times 10^{-9}$ is measured with an unbinned maximum likelihood fit. The measured branching fraction is in agreement with the expectation from the Standard Model. The observed number of $B^0\rightarrow μ^+μ^-$ candidates is consistent with the background expectation and an upper limit on the branching fraction of ${\cal BR}(B^0\rightarrow μ^+μ^-) < 9.4\times10^{-10}$ is obtained.
Rare heavy flavor decays provide stringent tests of the Standard Model of particle physics and allow to test for possible new Physics scenarios. The LHCb experiment at CERN is the ideal place for these searches as it has recorded the worlds largest sample of beauty mesons. The status of the rare decay analyses with 1\invfb of $\sqrt s = 7\tev $ of $pp$--collisions collected by the LHCb experiment in 2011 is reviewed. The worlds most precise measurements of the angular structure of \BdToKstmm decays is discussed, as well as the isospin asymmetry measurement in $\decay{B}{\kaon^{(*)} \mup\mun}$ decays. The most stringent upper exclusion limit on the branching fraction of \Bsmm decays is shown, as well as searches for lepton number and lepton flavor violating processes.
The current experimental status of the searches for the very rare decays $B^0_s \rightarrow μ^+ μ^-$ and $B^0 \rightarrow μ^+ μ^-$ is discussed. These channels are highly sensitive to various extensions of the Standard Model, specially in the scalar and pseudoscalar sector. The recent, most sensitive measurements from the CDF, ATLAS, CMS and LHCb collaborations are discussed and the combined upper exclusion limit on the branching fractions determined by the LHC experiments is shown to be $4.2\times 10^{-9}$ for $B^0_s \rightarrow μ^+ μ^-$ and $0.8\times 10^{-9}$ for $B^0 \rightarrow μ^+ μ^-$. The implications of these tight bounds on a selected set of New Physics models is sketched.