Bs->J/psiPhi analysis project

This is the new page of the Edinburgh Bs->J/psiPhi analysis project. The old page may be found here.


The Edinburgh LHCb team aims to deliver a self-contained analysis of the Bs->J/psiPhi decay and carry out a precise and reliable measurement of the weak mixing phase of the Bs system using LHCb data.

Meetings and Events

CP WG beta_s meeting Thursday 23 September 2010 link

Task lists and ideas to be exploited

  • Data-driven optimization of the offline event selection for best precision of the mixing phase: adapt Conor's CROP tool to minimze the figure of merit proposed by Yuehong. See Study of JpsiPhi offline selection

  • Flavour tagging monitoring and improvement: monitoring tagging performance using B+->JpsiK+ and Bd->JpsiK*; tune tagging algorithms for data with large number of interactions per event; train neural network on real data instead of MC data.

  • Understanding and improving time resolution.

  • Background study: understand background mass, proper time and angular distributions in real data and MC data; understand peaking background.

  • Fitting: deal with background and acceptance effects. Two programs exist. RapidFit relies on "standard" method to extract background distributions from sidebands and extract angular accepatnce from MC data; Yuehong's program uses "sFit" technique to subtract background in maximum likelihood fit and is designed to use angular acceptance from B+->JpsiK+, once enough data are accumulated.

  • Model testing: develop goodness-of-fit tests. Methods: visual check; binned Chi2 test; PDE methods; neural network method. The neural network method is appealing for multivariate fit as it needs no binning and is potentially sensitive to localized discrepancy. Basic idea: try to train a neural network to separte real data dn data generated using fitted model. If the trained network has separation power on test samples of real data and generated data, then the model is flawed.

  • Systematic uncertainties and model uncertainties.

  • inclduing S-waveand resolving sign of cos(2beta_s).

  • Longer term tasks: measurement of direct CPV mixing-incuded CPV in each polarization.

Current focuses

  • Playing with Collision10 data and develop method for data-driven optimization of offline selection
  • Understanding tagging performance in data using B+->JpsiK+
  • Understanding proper time reolsution using prompt Jpsi

Achievements and contributions


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Topic revision: r12 - 2010-09-16 - YuehongXie
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