Klaus Föhl, PANDA Cerenkov workshop in Glasgow, 11 May 2006 Disc DIRC

quick orientation for non-pandas brief particle ID motivation Cherenkov radiation flypast lightguides and simulations photo readout and B-field Plexiglass? Temperature! ToP Test Experiments the intended agenda...

the current GSI Gesellschaft für Schwerionenforschung

the new FAIR SIS 100/300 Facility for Antiproton and Ion Research planning as of 2004

Antiprotons at FAIR SIS 100/300 Panda HESR 1 GeV/c – 15 GeV/c planning as of 2004

PANDA Side View Pbar AND A AntiProton ANihilations at DArmstadt

Particle ID in PANDA

5 degrees 22 degrees Particle ID in PANDA

Particle ID & Kinematics pp  KK T=5,10,15 GeV/c pp  DD D  K  T=6.6 GeV/c pp i.e. charmonium production need to measure two quantities: dE/dx energy momentum velocity momentum (tracking in magnetic field) velocity (Cherenkov Radiation) momentum (tracking in magnetic field) velocity (Cherenkov Radiation) if mass known, particle identified K      K K    K even or K     distinguish  and K (K and p)... D For what channels do we not have this factor 2-3 reduction?

Cerenkov Radiation prism: correcting dispersion lens: turning angle into position  parallel light paths chromatic dispersion  =1  <1 Cerenkov angle depends on particle speed  the cone gives a ring image on a detector plane material with a different dispersion

4-fold direction ambiguity angle and edges crucial 2-fold ambiguity in disc, lifted at readout only parallel surfaces required DIRC: BaBar-type versus Disc

conserving angles and circles 90 degrees 45 Solid Angle onto flat surface

conserving angles and circles 90 degrees 45 Light transmitted in DISC

conserving angles and circles 90 degrees 45 Colour fringes on rings

90 degrees 45 coordinates measured at rim

90 degrees 45 3-prong event in DISC

LiF side view front view fused silica LiF polynomial coefficients: c2= -3.0/(60^2) c3= -0.5/(60^3) c4= -0.1/(60^4) focussing is better than 1mm over the entire line chosen as focal plane side view fused silica completely within medium all total reflection compact design all solid material flat focal plane DIRC Detector Idea 5cm

Location Changes

Lightguide-Designs polynomial coefficients: c2= -3.0/(60^2) c3= -0.5/(60^3) c4= -0.1/(60^4) focussing is better than 1mm over the entire line chosen as focal plane polynomial coefficients: c2= -5.4/(60^2) c3= -0.9/(60^3) c4= -0.5/(60^4) possibly difficult design requirements: 1)vertical focal plane (normal to B-field) 2)short focal plane (high dispersion deg/mm)

Status of simple Disc Simulations –perfect surfaces –proper directions recent improvements –true 3D –analysis of pixel hits in the pipeline –angular straggling -important for (e,  ) and ( ,  ) –further optimising –include upstream tracking (necessary?) NOT: –no diffraction –no polarisation –no background (particles and photons) –no maximum likelihood analysis –not free of minor approximations (KISS)

status of simulations vertex provided position provided all from DISC data 64 lightguides (no pixels) 128 (no pixels) nondispersive materials fluctuations numerical artefact - it’s on the “to do” list... unpixelised focal plane no chromatic correction REALLY PRELIMINARY

further optimisation resolution scaling with pixels resolution not scaling with pixel size (momentum resolution) ~ (pixel number * quantum efficiency) 4

Yoke Solenoid Housing Solenoid and Yoke Environment

Photon Detectors phototubes APDs channel plate phototubes optical fibres and external phototubes HPDs with magnetic imaging

Position-sensitive Phototubes H8500 H9500 R cm B-field probably too strong

Yoke Light guide or fibre readout?  determination determination

HPD with magnetic imaging Klaus Föhl 2-June-2004

fused silica E B Silicon Strip Detector e - photocathode HPD readout possible? fused silica E B photocathode Silicon Strip Detector e - possibly higher quantum efficiency in reflective photocathode geometry

Temperature cold solenoid, cold EMC maybe coolde APDs SiO2, LiF different expansion coefficients dew, condensation on surfaces

Yoke Radiation Countermeasures? what radiation fields? do we need radiation shielding? will PB act:- -as absorber -or as converter?

Plexiglass as Cerenkov radiator? maybe not such a stupid idea transmission –SiO nm N 0 /mm=14 –plexi nm N 0 /mm= 7 radiation hardness –BaBar “Spectrosil” proven –plexiglass “hamm wer doa” not proven but: radiation length X 0 three times larger –36cm versus 12cm (40.5g/cm2 vs 26g/cm2)  more photons per X 0  less chromatic dispersion  no UV-grade material necessary (glass, glue, PMT) –focussing optics probably ok for thicker radiator –availability? time stability? radiation hardness? higher lower dispersion maybe not such a stupid idea

Time-of-Propagation in a dispersive medium fused silica (aka quartz) 2% 6% Light propagation speed perpendicular to Cherenkov-light-emitting particle track: =300nm photon is 6% slower than 600nm larger Cherenkov angle – 2% shorter path  4% time difference ( =600nm is “faster”)  difference equivalent to  =0.04 for 120cm radial distance ToP=8.3ns (400nm)  0.33 ns spread in arrival time

ToP in DISC – some thoughs... chromatic time correction – do not see how (I see no space for red light to run extra length) (unless photon detector timing can be made colour-dependent) disc not self-timing “GPS altitude problem” external time reference should be 100ps/sqrt(N) if time reference from target vertex  factor 2 better  overall situation equivalent to 4.5 metres TOF >>50*multiplicity pixels needed multiple hits can be separated if spaced apart

Towards Test Experiments Radiator slab (fused silica, plexiglass) Focussing lightguide –Edinburgh workshop: perspex: ok quartz: we are happy to try (difficulties anticipated) photon readout DAQ

Conclusions?

Material Test Testing transmission and total internal reflection of a fused silica sample (G. Schepers and C. Schwarz, GSI)

FAIR international accelerator facility Particle ID – the physics requirements Cerenkov Radiation DIRC in PANDA Detector performance Conclusions and Outlook Outline working on Cerenkov detectors for PANDA: Edinburgh, GSI, Erlangen, Gießen, Dubna, Jülich, Vienna, Cracow, Glasgow

Pion-Kaon-Separation   K K K threshold centre hole figure of merit N = 152cm N(ideal) = N x 1cm x sin ( ) = 82 geometric transmittance N(detected) = 82 x 0.61 = fused silica plate 10mm thickness (density 2.2g/cm thus 8% radiation length) detection efficiency 20% ( = nm ) 0 64 segments in  each with 48 rectangular pixels overall 3072 pixels

Conclusions optical properties of this design are good enough performance depends on number of pixels optical test bench phototubes + electronics operational detector slice testbeam experiments

Side View 10mm fused silica plate (density 2.2g/cm, 8% radiation length) plate radius 1500mm, detection plane radius 2000mm wavelength range nm, detection efficiency 20% figure of merit N = 152cm N(ideal) = N x 1cm x sin ( ) = 82 N(detected) = 82 x 0.61 = 50 geometry transmittance mm 2000mm

Photon Lines in  space   target particle vertices point

Lensing cylinder lense N.B. to be compared with 10mm pixel height spread over prism width

Chromatic Correction higher dispersion glass spread =300nm to 600nm

Lensing cylinder lense N.B. to be compared with 10mm pixel height spread over prism width

Chromatic Correction higher dispersion glass spread =300nm to 600nm

Chromatic Correction higher dispersion glass effective pixel height spread =300nm to 600nm +

Cherenkov radiation wavefront Poynting vector c

Cherenkov radiation in a dispersive medium wavefront Poynting vector c

Cherenkov radiation in a dispersive medium fused silica (aka quartz) 2% 6%

Momentum Thresholds fused silica n=1.47 aerogel n=1.05 K K p p  total internal reflection limit n=1.47 K p  

tracks in Solenoid field solenoid field taken to be homogenous within the real field shape the particles are better aligned with the field lines

fused silica B. Morosov, P. Vlasov et al. December 2004 fused silica LiF side view front view fused silica LiF

adjusting polynomial coefficients (c2 fixed, c3 and c4 so far used only) to find a mirror shape that provides overall acceptable focussing along a straight line (easier to instrument) concurrent optimisation goals minimise: lensing errors warping of focal plane 1. 2.

conserving angles and circles

side view fused silica polynomial coefficients: c2= 1/1200 c3= -0.5/(60^3) c4= -0.1/(60^4) focussing is better than 1mm over the entire line chosen as focal plane completely within medium all total reflection compact design all solid material flat focal plane

Particle ID in PANDA 5 degrees 22 degrees For particle ID, two quantities are required: dE/dx energy momentum (tracking in magnetic field) velocity (Cherenkov Radiation) If particle mass is known, the particle is identified. For particle ID, two quantities are required: dE/dx energy momentum (tracking in magnetic field) velocity (Cherenkov Radiation)

briefly on Barrel-DIRC time-of-propagation version Klaus Föhl, FAIR-Panda-PID-meeting, 5/12/2005

Cherenkov radiation in a dispersive medium  =0.95  =1 incident particle at 45 degrees fused silica slab 3m long =600nm =300nm correction1 =300nm =300nm correction2  =0.99

Cherenkov radiation in a dispersive medium fused silica (aka quartz) 2% 6% reduce wavelength range to improve sensitivity

dispersion correction correction needs to cover entire angular range of incident particles

dispersion correction no correction improving over the entire angular range

my conclusions Barrel-DIRC photon group velocity in dispersive medium photon detector number set by statistics dispersive correction not covering all relevant angles reference timing provided by first arriving photons standard PMT timing is enough consider to cut out <400nm photons/pixel << 1 most stringent requirement configuration angle-dependent useless for the barrel no external timing required to analyse barrel DIRC data