CP violation in the B system

The phenomenon of CP violation is crucial to understand the asymmetry between matter and antimatter that exists in the Universe. Dramatic experimental progress has been made, in particular in measurements of the behaviour of particles containing the b quark, where CP violation effects are predicted by the Kobayashi-Maskawa mechanism that is embedded in the Standard Model. The status of these measurements and future prospects for an understanding of CP violation beyond the Standard Model are reviewed.Comment: Invited review for Rep. Prog. Phys. v2 corresponds to published versio

Real-time data analysis at the LHC: present and future

The Large Hadron Collider (LHC), which collides protons at an energy of 14 TeV, produces hundreds of exabytes of data per year, making it one of the largest sources of data in the world today. At present it is not possible to even transfer most of this data from the four main particle detectors at the LHC to "offline" data facilities, much less to permanently store it for future processing. For this reason the LHC detectors are equipped with real-time analysis systems, called triggers, which process this volume of data and select the most interesting proton-proton collisions. The LHC experiment triggers reduce the data produced by the LHC by between 1/1000 and 1/100000, to tens of petabytes per year, allowing its economical storage and further analysis. The bulk of the data-reduction is performed by custom electronics which ignores most of the data in its decision making, and is therefore unable to exploit the most powerful known data analysis strategies. I cover the present status of real-time data analysis at the LHC, before explaining why the future upgrades of the LHC experiments will increase the volume of data which can be sent off the detector and into off-the-shelf data processing facilities (such as CPU or GPU farms) to tens of exabytes per year. This development will simultaneously enable a vast expansion of the physics programme of the LHC's detectors, and make it mandatory to develop and implement a new generation of real-time multivariate analysis tools in order to fully exploit this new potential of the LHC. I explain what work is ongoing in this direction and motivate why more effort is needed in the coming years.Comment: Contribution to the proceedings of the HEPML workshop NIPS 2014. 20 pages, 5 figure

Measurement of CPCP observables in Bs0→Ds∓K±B_s^0 \rightarrow D_s^{\mp}K^{\pm} at LHCb

The time-dependent CP-violating observables accessible through Bs->DsK decays have been measured for the first time using data corresponding to an integrated luminosity of 1 inverse fb collected in 2011 by the LHCb detector. Using these observables, the CKM angle gamma is determined to be (115 -43 +28) modulo 180 degrees at 68% CL, where the uncertainty contains both statistical and systematic components.Comment: Proceedings of the 8th International Workshop on the CKM Unitarity Triangle (CKM 2014), Vienna, Austria, September 8-12, 201

Performance of the LHCb High Level Trigger in 2012

The trigger system of the LHCb experiment is discussed in this paper and its performance is evaluated on a dataset recorded during the 2012 run of the LHC. The main purpose of the LHCb trigger system is to separate heavy flavour signals from the light quark background. The trigger reduces the roughly 11MHz of bunch-bunch crossings with inelastic collisions to a rate of 5kHz, which is written to storage.Comment: Proceedings for the 20th International Conference on Computing in High Energy and Nuclear Physics (CHEP

Measuring direct CP violation in four body baryonic B decay modes at LHCb

Baryonic B decays may allow direct measurements of CP violation at LHCb. Direct CP violation in the decay mode B+ -> ppK*+ has been predicted to be 22% in the Standard Model, while it is predicted to be only 1% in B0 -> ppK*0. Both modes are believed to proceed through penguin diagrams, making them sensitive to new physics effects which could significantly alter the observed level of CP violation. LHCb's potential to observe CP violation in these decay modes is discussed. The decay mode B+ -> ppK*+ is expected to yield approx. 400 and B0 -> ppK*0 approx. 1600 signal events with 2fb^-1 of data taking. LHCb can expect to measure CP violating asymmetries with a precision of approx. 7% in B+ -> ppK*+ and approx. 3.5% in B0 -> ppK*0 with 2fb^-1 of data taking, and these measurements are not expected to be systematics limited

Quark flavour physics: status and future prospects

Quark flavour physics is the study of hadrons, their properties, and their decays into other particles. As a discipline it simultaneously catalogues the nature of physical states within the Standard Model of particle physics, and in doing so tests the consistency and completeness of the Standard Model's description of reality. Following the discovery of the Higgs field, it is more essential than ever to critically examine the Standard Model's own coherence. Precision studies of quark flavour are one of the most sensitive experimental instruments for this task. I give a brief and necessarily selective overview of recent developments in quark flavour physics and discuss prospects for the next generation of experiments and facilities, with an emphasis on the energy scales of beyond Standard Model physics probed by these types of measurements.Comment: Invited review for IJMP

Monte Carlo Independent Lifetime Fitting at LHCb in Lifetime Biased Channels

Lifetime measurements at LHCb will help in detector calibration as well as providing constraints on lifetime differences in the $B_s$ system and other theoretical models. In order to exploit the full range of decays available in LHCb, it is important to have a method for fitting lifetimes in hadronic channels, which are biased by the impact parameter cuts in the trigger. We have investigated a Monte Carlo simulation independent method to take into account the trigger effects. The method is based on calculating event by event acceptance functions from the decay geometry and does not require any external input. This note presents current results with this method for both the full LHCb Monte Carlo for the channel $B^{0}_{d} \rightarrow D^{-} \pi^{+}$ and a toy Monte Carlo for the same channel, including a discussion of the expected statistical precision on lifetime measurements using this method once LHCb is operational

A Monte Carlo simulation free method of measuring lifetimes using event-by-event acceptance functions at LHCb

A set of innovative methods and tools for precision lifetime and lifetime-difference measurements in hadronic B decays at LHCb is presented. All methods are purely data-driven and Monte Carlo simulation independent, a particularly important feature if lifetime measurements are to be made in the early period of LHCb's data taking. The methods and tools are shown to work in detailed simulation studies, including both Toy and Full Monte Carlo simulation studies of possible systematic biases in the measurements

New approaches for boosting to uniformity

The use of multivariate classifiers has become commonplace in particle physics. To enhance the performance, a series of classifiers is typically trained; this is a technique known as boosting. This paper explores several novel boosting methods that have been designed to produce a uniform selection efficiency in a chosen multivariate space. Such algorithms have a wide range of applications in particle physics, from producing uniform signal selection efficiency across a Dalitz-plot to avoiding the creation of false signal peaks in an invariant mass distribution when searching for new particles.National Science Foundation (U.S.) (Grant PHY-1306550

On the interplay of direct and indirect CP violation in the charm sector

Charm mixing and CP violation observables are examined in the light of the recently reported evidence from LHCb for CP violation in the charm sector. If the result is confirmed as being due to direct CP violation at the 1% level, its effect will need to be taken into account in the interpretation of CP violation observables. The contributions of direct and indirect CP violation to the decay rate asymmetry difference DeltaACP and the ratios of effective lifetimes AGamma and yCP are considered here. Terms relevant to the interpretation of future high precision measurements which have been neglected in previous literature are identified.Comment: accepted for publication in J. Phys.