Bs J/psi phi

This page contains information on the Bs -> J/psi phi analysis. All ATLAS B-Physics meeting can be found in indico here.

2011 data paper status (ATLAS-BPHY-2013-01-001)

2012 data paper status (ATL-COM-PHYS-2014-598)

Other results

BLUE combination

The Best Linear Unbiased Estimator (BLUE) method is what we are using to combine the 2011 and 2012 datasets.

2D contour plots

The 2D contour plots show the statistical errors only. It should therefore be possible to combine them both simply by adding the likelihood together. The code is not currently in SVN (Sept 14) and is in /Users/dewhurst/WorkArea/ContourPlots on my laptop. To run:
root[] gROOT->LoadMacro("AtlasStyle.C");
root[]  SetAtlasStyle();
root[] .L plot_2D_scan_Minuit.2.cpp+
root[] plot_2D_scan_LikelihoodScan_phiSdeltaG()

Bs J/psi phi code

At the end of June 2013 a series of tutorial were held to teach people how to run the code for the Bs to J/psi phi analysis:

To check out the code:

svn co svn+ssh:// BsJpsiPhiAlgs

xAOD development

MC Event Generation

List of MC datasets

Real data

List of real datasets

Bd Mass difference measurement

The Bd mass difference Delta M_d has been measured precisely by several of the B-Factory experiments as well as LHCb. The reason for ATLAS to measure it is to calibrate our tagging measurement.

A List of useful papers:

Analysis method

The analysis method is fairly straight forward. In order to measure the mass difference we need to know the asymetry which can be measured if we know the inital and final flavour of the B meson. The final flavour is fixed because of the reconstruction algorithm. The intial flavour is identified using the tagging method we want to calibrate.

Event selection

  • The intial flavour of the B meson needs to be tagged.
  • Usual J/psi + K0* selection cuts
  • Extra cut on a window around Bs -> J/psi phi mass (using K+ K- mass hypothesis) to remove Bs -> J/psi phi events.
  • Lifetime cut to remove prompt J/psi events?

Maximum Likelihood

  • Gaussian with event by event errors for signal mass
  • Second order polynomial for background mass

Norway tutorial

Notes on Norway computing tutorial * Indico link

Site Configuration

This section includes information about how best to configure sites.

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Topic revision: r32 - 2014-10-30 - AlastairDewhurst
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