HFAG-charm averages

The extraction of charm mixing and CP violation parameters requires the combination of many measurements. The latest averages are reviewed and the contribution of individual measurements is discussed. While it is established that the CP-even eigenstate is the shorter lived, the oscillation frequency of charm mesons is still not known to high accuracy. All CP asymmetries are found to be compatible with zero within less than 3 sigma.Comment: Proceedings of the 8th International Workshop on the CKM Unitarity Triangle (CKM 2014), Vienna, Austria, September 8-12, 201

The charm physics programme at the LHCb upgrade, and Atlas and CMS upgrades

Charm physics has been established at the LHC based on several high-precision measurements. The future of charm physics at the LHC experiments is discussed in detail. The bulk of the charm physics programme will be performed by LHCb and the LHCb upgrade. In particular, the impact of the LHCb upgrade on mixing and \CP violation measurements is presented.Comment: to appear in the proceedings of The 5th International Workshop on Charm Physics (Charm 2012

Introduction to Charm Physics

This paper gives an overview of charm physics. It is a lecture write-up aimed at students with a minimum of prior knowledge in particle physics, but at the same time provides a state-of-the art review of the field. The main focus is on mixing and CP violation, which is a field with ever growing attention since first evidence for charm mixing was observed in 2007. Other areas covered are charm spectroscopy, production, as well as rare decays.Comment: 39 pages, 11 figures. Proceedings of the workshop "Flavorful Ways to New Physics", October 28-31 2014, Freudenstadt, German

Alignment of the LHCb Vertex Locator

LHCb will commence data taking as the first dedicated heavy flavour experiment at a hadron collider in 2008. A very high hit precision from its vertex detector (VELO) is essential to meet the tight requirements of vertex reconstruction in B-physics. The single hit precision of the VELO is better than 10 micron. However, the VELO is operated only 8 mm from the beam and must be retracted and reinserted each LHC fill. Hence, the detector places unique demands on its alignment algorithm. The partially assembled VELO system has already been tested in a beam test. The novel software alignment methods are presented together with their interplay with the metrology measurements. Results from Monte Carlo simulation studies are discussed and recent beam test results are shown that prove the method's precision at the micron level.Comment: Presented at the 10th International Conference On Instrumentation For Colliding Beam Physics (INSTR08), 28 Feb - 5 Mar 2008, Novosibirsk, Russi

Searches for CP Violation in Charm Mixing at LHCb

LHCb has started its charm physics programme using the data taken at the LHC. The first measurements of open charm production cross-sections for proton proton collisions at \sqrt{s}=7 \tev are presented. The cross-sections of the \PDzero, \PDstar^+, \PDplus, and \PDsplus mesons are found to be in broad agreement with theory predictions. The prospects for measurements of charm mixing, CP and T violation in decays of neutral \PD mesons at LHCb are discussed. Furthermore, plans for CP violation measurements using charged \PD mesons are presented. Most analyses are expected to yield results improving the current world averages based on the data expected to be taken in 2011.Comment: Proceedings of CKM2010, the 6th International Workshop on the CKM Unitarity Triangle, University of Warwick, UK, 6-10 September 201

What did we learn in theory from the Delta ACP Saga?

The measurement of CP violation in the charm sector triggered a lot of theoretical activities and re-considerations. Nevertheless currently neither theory nor experiment have reached definite conclusions about the origin of a large CP violating effect in hadronic D decays. We review briefly (part of) the current theory literature and present as the most important outcome of the many investigations initial steps in a long journey to understand the standard model contribution to hadronic D meson decays from first principles as well as various control channels, that can be studied by experiment

Alignment of the LHCb Vertex Locator and lifetime measurements of two-body hadronic final states

Lifetime measurements offer excellent opportunities for precision tests of the Standard Model of Particle Physics as well as for discovery of effects involving particles beyond the Standard Model. This thesis presents a method for measurements of lifetimes and lifetime ratios and its application to two-body hadronic final states of heavy flavour decays at LHCb. The LHCb experiment is designed to measure heavy flavour particle decays produced in proton-proton collisions at the LHC. Key to high quality vertexing is the spatial alignment of the Vertex Locator. The algorithms designed for this task, including a novel approach for the relative sensor alignment, are discussed in detail. Their performance is presented using test beam data as well as data using the first beam induced tracks from LHC. The precision of these algorithms is found to be of the order of 1-2 microns. A method for lifetime fitting using a Monte Carlo independent approach to determine a lifetime acceptance function on an event-by-event basis is presented. These acceptance functions are crucial to account for a bias caused by the trigger selection. The un-binned maximum likelihood fitter based on this method does not rely on a parametrised model for the lifetime distribution of combinatorial background. The fit of the lifetime measured in Bs->K+K- decays using a simulated data sample equivalent to an integrated luminosity of 0.1/fb would yield tau(Bs->K+K-) = (1.498+/-0.030(stat.)+/-0.005(syst.))ps with an average input lifetime of 1.500ps. A competitive measurement of DeltaGamma_s extracted from the Bs->K+K- lifetime measurement would require a data set equivalent to about 0.7/fb of luminosity. With an integrated luminosity of only about 0.03/fb it will be possible to make a competitive measurement of the D mixing parameter y_CP. This uses a lifetime ratio measurement with prompt D->h+h'- decays. A first event selection for prompt D->h+h'- decays is presented. The major hurdle for this measurement is the contribution from secondary D decays. Possible solutions are discussed

GPU-based optical photon simulation for the LHCb RICH 1 Detector

We present the investigation of the use of Opticks, a GPU-accelerated optical photon interface with the LHCb detector simulation, to improve computation time of optical photon propagation. The hybrid workflow, combining the particle simulation package Geant4 and Opticks, offloads optical photon propagation to GPUs, thereby accelerating the overall simulation process. The consistency of the results obtained from Geant4 and Opticks simulations is verified with a simplified LHCb RICH 1 detector geometry, demonstrating the feasibility of the proposed approach. In addition, the ongoing transition to the NVIDIA OptiX 7 API and re-structuring of Opticks code is discussed within the context of HEP simulation workflows, with caveats explored

On model-independent searches for direct CP violation in multi-body decays

Techniques for performing model-independent searches for direct CP violation in three and four-body decays are discussed. Comments on the performance and the optimisation of a binned chisquare approach and an unbinned approach, known as the energy test, are made. The use of the energy test in the presence of background is also studied. The selection and treatment of the coordinates used to describe the phase-space of the decay are discussed. The conventional model-independent techniques, which test for P-even CP violation, are modified to create a new approach for testing for P-odd CP violation. An implementation of the energy test using GPUs is described

Optical Photon Simulation with Mitsuba3

Optical photon propagation is an embarrassingly parallel operation, well suited to acceleration on GPU devices. Rendering of images employs similar techniques -- for this reason, a pipeline to offload optical photon propagation from Geant4 to the industry-standard open-source renderer Mitsuba3 has been devised. With the creation of a dedicated plugin for single point multi-source emission, we find a photon propagation rate of $2\times10^{5}$ photons per second per CPU thread using LLVM and $1.2\times10^{6}$ photons per second per GPU using CUDA. This represents a speed-up of 70 on CPU and 400 on GPU over Geant4 and is competitive with other similar applications. The potential for further applications is discussed.Comment: 7 pages, 8 figure