LHCb RICH Performance in Brunel Development Version v27r3

Introduction

This page presents the LHCb RICH detector performance data for the development version of Brunel v27r3. This version is similar to the RTTC05 compatibile production, but is the first version to incorporate a new tuning of the RICH offline reconstruction (see here for details).

The results shown below were produced using a privately generated sample of 20K B inclusive (event type 10000000) events.

The software versions used where :-

• Gauss v19r4
• Boole v8r4
• Brunel v27r3

Raw ROOT files and Figures for download

Only a selection of performance figures are shown on this page. All figures are though available for download, in both png and eps formats. In addition the raw ROOT histogram files are also available. See here for available data files. The ROOT macros used to produce the images are also available.

Core Track Resolutions

These section contains some figures showing the resolutions obtained from the various Track types at the entrance and exit points to each of the RICH radiator media. These resolutions feed directly in the Cherenkov theta resolutions shown in the proceeding sections.

• Forward Tracks
• Match Tracks
• Seed Tracks
• VeloTT Tracks
• Ks Tracks

Cherenkov Theta Angle Resolution

Forward Tracks CK Theta Resolution

The following images show the Cherenkov theta resolutions obtained in the RTTC05 data production, for forward tracks only (for other track types, see the attached image tar files). The resolution is defined as the difference between the reconstruction cherenkov theta angle for a given track and pixel pair, and the expected Cherenkov angle for the given track in the radiator medium (based on the reconstructed track parameters).

Note, if you require eps format images, these can be found in the image tar files available here.

VeloTT Tracks CK Theta Resolution

For comparison, the same plots for VTT tracks (in aerogel and C4F10 only).

Cherenkov Photon Yields

The following figures show the distributions for the number of detected unscattered Cherenkov photons in each of the radiator media. Only saturated tracks (beta>0.99) were used.

Note, if you require eps format images, these can be found in the image tar files available here.

C4F10 photons per track" width="567" height="384" />

PID Performance versus Track Momentum

Overall Track Performance

The following figures show the RICH particle identification performance, as a function of momentum, for forward tracks and match tracks. No cuts on the delta Log-Likelihood values are applied; tracks are ID using the "best" measure, i.e. the mass hypothesis that gave the minimum overall likelihood. The figures of merit used are the RichHeavyID, RichLightID, RichKaonID and RichPionID identifications for the 2 to 100 GeV momentum range.

For images for other track types, see the attached image tar files.

Forward Tracks PID Performance

Heavy and Light ID :-

The following images are for explicitly identifying kaons as kaons and pions as pions :-

Match Tracks PID Performance

Heavy and Light ID :-

The following images are for explicitly identifying kaons as kaons and pions as pions :-

Positive and Negative Track Comparisons

The following images gives a comparison of the RichHeavyID and kaon performance for positive and negative tracks. The figures was produced for all track types combined. Currently the comparision is statistics limited; No difference can be seen between the positive and negative tracks. However, a small difference is expected and thus larger statistics studies will follow.

Note, if you require eps format images, these can be found in the image tar files available here.

Individual Performance in each RICH Detector and Radiator Media

The following figures given the RichHeavyID performance as a function of track momentum when only one of the two RICH detectors are used and for RICH1 when only aerogel or the C4F10 radiators are considered. The information from the other radiators are simply ignored. As with the previous performance curves, only forward tracks are included.

Note, if you require eps format images, these can be found in the image tar files available here.

C4F10 radiator only, for forward tracks" width="567" height="384" />

Breakdown of Performance by Radiator Medium

The following figure compares the individual performance in each radiator medium with that obtained overall when the information from all radiators are combined.

The red points are the K->K,Pr efficiency whilst the blue points represent the pi->K,Pr mis-identification rate. The solid points give the overall performance when all radiators are combined, whilst the open crosses, squares and triangles give the individual performance in the aerogel, C4F10 and CF4 radiators respectively.

Note, if you require eps format images, these can be found in the image tar files available here.

Reference Log Files

The following are reference logs files from the RICH reconstruction.

• allrads-newTune-10000000.log: Log file for RICH reconstruction. All radiators Brunel v27r3.

• rich1-newTune-10000000.log: Log file for RICH reconstruction. RICH1 only Brunel v27r3.

• rich2-newTune-10000000.log: Log file for RICH reconstruction. RICH2 only Brunel v27r3.