The investigation of the fluctuations of the alignment constants of Inner Tracker (IT) stations in magnetic field (for two polarisations - Up and Down) on 2011 and 2012 data samples was performed. In the process of study was done a some tests: convergance test and alignment time dependence test.
The convergance test: The Tx discrepancy with official parameters from database (DB) is up to 60 um for 2011 and 2012 data and is below 20 um for 2011 simulation data. These results are within the IT spacial resolution. The difference in Tx between two magnetic field polarisations is about 25 um. Therefore, there is no strong evidence of detector positions dependence on magnetic filed polarisation.
The alignment time dependence test. Good agreement with official alignment for configuration with loose Tx constraints for OTCFrames and fixed OTModules is obtained for data in both polarisations. The observed fluctuations over time in one data period are up to 60 um and in agreement with detector resolution. No discrepancy is observed between Up and Down polarisations for analyses data. Observed fluctuations of alignment parameters don't have a significant impact on physical observables like resonance masses or their width. The difference between nominal and realigned IT parameters for JPsi sample is two to three times larger than in D0 sample.
All results were presented on Tracking and Alignment meeting of LHCb. The presentations are located in Talks.
The studies of the effect magnet polarity on the alignment of the IT Stations present on LHCb twiki page.
The study presents a method of the measurement of CP-violating phase phi_s using the B0s meson decay B0s->JPsiPhi. The determination of phi_s is one of the key measurements of the physics program of the LHCb experiment. The phase phi_s arises from the interference between B0s mixing and the decay and is predicted by the Standard Model to be phi_s = (-0.0364+-0.0016) rad [link to paper]. Physics processes beyond the Standard Model can affect the B0s mixing amplitude and lead to deviations from this prediction. The precision measurement of phi_s therefore constitutes an indirect search for New Physics.
The phase was most precise measured in B0s->JPsi(->mu+mu-)K+K- and B0s->JPsi(->mu+mu-) pi+pi- decays and consisted phi_s = 0.01+-0.07(stat)+-0.01(syst) rad but the measurement of phi_s has large systematic and statistical uncertainties [link to paper]. To reduce the uncertainties and increase precision of the measurement phase phi_s the study of B0s->JPsiPhi decay where JPsi->e+e- is performed.
The stage of the investigation:
The analysis status of B0s->JPsi(ee)Phi decay present on LHCb twiki page.
Meerkat is the multidimensional kernel density estimation package. It uses a variation of kernel density estimation (KDE) technique, relative KDE, where kernel density provides the correction on top of some approximation PDF. The approximation PDF defines the behaviour of the resulting PDF estimate at the edges of the phase space and in the region of rapidly-changing structures. This approach allows to use kernel density estimation in a multidimensional case, for the phase spaces with have non-trivial boundaries (such as for Dalitz plots). Link to Meerkat documentation here.
The purpose of the Calorimeter Objects Tools Group is to provide support to users for the calorimeter-related analysis. The group will provide performance tables, plots as well as instruction for the usage of the various calorimeters objects : photon & neutral pions, converted photons, BremStrahlung corrections, charged and neutral identification and MC-related issues. Link to LHCb twiki page here.
The participation in the Data Manager shifts (in charge of online data monitoring and quality control) and Calo piquet shifts (in charge of ECAL, HCAL and SPD detectors).