Difference: BarrelDirc (r9 vs. r8)

Purpose

the DIRC provides

  • a positive kaon identification
  • a destinction of gammas and relativistic charged particles entering the EMC behind him

Working principle

  • Cherenkov Detector
  • determination of the mass of the particle by combining his velocity information with momentum information from the tracking detectors

Important values

  • Polar angle vs. momentum distribution of the kaons in radiative decays of resonances in formation experiments like J/psi -> K+K- gamma for the search of glue-balls (Ref. TPR):

Polar angle vs. momentum distribution of the kaons in radiative decays of resonances in formation experiments like J/psi -> K+K- gamma for the search of glue-balls.

  • the barrel DIRC covers the solid angle of 22 to 140 degrees
  • the lower momentum threshold for kaons which produce Cherenkov light is for an envisaged refractive index of n=1.47 as low as 460 MeV/c (for single photon producton -- for photon numbers bigger than 4 it is more than 200 MeV/c higher)

FIRST Estimations:

  • Single Photon Cherenkov Angle Resolution
  • with a DIRC-Bar size of 17x30x2000mm, a distance of l=1.20m of the photomultipiers from the bar exit and a diameter of the photomultiplier cathods of 2cm ( beeing equal to the distance of the centers of the cathods) the geometric contribution of the Single Photon Cherenkov Angle Resulution can be calculated and lies in the order of magnitude of 10mrad
  • to this geometric contribution the resolution contribution (comming from the production and the transmission dispersion) has to be added which has a values of similar size
  • Correlation of Cherencov Cherenkov angle thetaCh Theta c as a function of laboratory momentum in the DIRC detector. The arrows mark a resolution of 10mrad.:
    Correlation of Cherencov angle Theta c as a function of laboratory momentum in the DIRC detector. The arrows mark a resolution of 10mrad.Correlation of Cherencov angle Theta c as a function of laboratory momentum in the DIRC detector. The arrows mark a resolution of 10mrad.
  • The resolution of the track Cherenkov angle sigma_trackshould scales scale with the square root of the number of photons detected:

sigma_track sigma_track(theta) = sigma_single sigma_single(theta) / sqrt(N_ph)

  • Identification Efficiency Thus we find approximatively the separation of two particle species, i.e. numbers of sigma (N(sigma)), with masses m1 and m2 (Ref. PDG): for Kaons and pions (Ref. CDR):
    Identification Efficiency for Kaons and pions

N(sigma) ~= |m1*m1 - m2*m2| / (2 * p*p * sigma_track(theta) * sqrt(n*n-1))

  • To provide usefull results the DIRC should produce 15 to 20 photons per particle track. The correlation calculated with a photon number of 16 is shown in the figure bellow.
  • Correlation between number of sigma's of seperation N(sigma) and the momentum of the particles for 16 photons per track and a single photon angle resolution of 10mrad.:
    Number of sigma's of seperation
  • Identification Efficiency for kaons and pions (Ref. CDR):
    Identification Efficiency for Kaons and pions
  • It is show the probability to misidentify a pion as a kaon as a function of the particle momentum (red circles) and the efficiency to identify a kaon (open circles)
  • Material Budget:
  • with 17mm (of thickness) of fused silica the DIRC bars present approximately 14% of a radiation length to normal incident particles particles. The support structure will add some more percent.

-- GeorgSchepers- 25 Apr 05 May 2006

IAttachmentActionSizeDateWhoComment
corr_ang_mom.gifcorr_ang_mom1.jpggif jpg corr_ang_mom.gif corr_ang_mom1.jpg manage4.2 42.0 K 25 Apr 05 May 2006 - 08:46 16:10 GeorgSchepers Correlation of Cherencov angle Theta c as a function of laboratory momentum in the DIRC detector. The arrows mark a resolution of 10mrad.
identification_alone.gifcorr_ang_mom2.jpggif jpg identification_alone.gif corr_ang_mom2.jpg manage12.1 31.7 K 25 Apr 05 May 2006 - 09:31 16:11 GeorgSchepersIdentification Efficiency for Kaons and NUmber of sigma's of seperation pions
kkgamma.gifidentification_alone.gifgifkkgamma.gif identification_alone.gif manage61.4 12.1 K 19 25 Apr 2006 - 13:50 09:31 GeorgSchepersPolar angle Identification Efficiency vs. momentum distribution of the kaons in radiative decays of resonances in formation experiments like J/psi -> K+K- gamma for the search of Kaons and pions glue-balls.
kkgamma.gifgifkkgamma.gifmanage 61.4 K 19 Apr 2006 - 13:50GeorgSchepers Polar angle vs. momentum distribution of the kaons in radiative decays of resonances in formation experiments like J/psi -> K+K- gamma for the search of glue-balls.

View topic | View difference side by side | History: r11 < r10 < r9 < r8 | More topic actions
 
This site is powered by FoswikiCopyright © by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
Ideas, requests, problems regarding PANDA Wiki? Send feedback
Imprint (in German)
Privacy Policy (in German)