Crystal Technologies for LC Ren-yuan Zhu Caltech International Workshop on Linear Collider Sitges, Barcelona, Spain May 3, 1999 Design Considerations for Calorimeter at LC. What Can Crystal Calorimetry Offer? Possible Crystal Technologies for LC: Oxides: from BGO to PbWO ; Halides: from CsI to PbF.
Design Considerations for Calorimetry at LC re- Precision measurement of electrons and photons: e/ lated physics. Electromagnetic energy resolutions; Position and photon angular resolutions; e/ identification and reconstruction efficiency. Good missing energy resolutions: /SUSY related physics. Hermeticity. Good jet energy resolution: jet related physics. Achievable jet resolution and intrinsic limitation; Dead material (coil?) in the middle of a calorimeter; Jet resolution improvement by using other detector components; Jet resolution improvement by using kinetic constraints: Z mass and center of mass. Dense absorber: a compact and cost effective calorimeter.
, T - e 5 ' Þ Ü S PQR ON IJKML HGF EDC Discovery Power of Precision e & Study quarkonium system through inclusive photons by Crystal Ball and CLEO. ˆ ˆ ˆ 6879 :;!!! η< " # # = >? @A ηb $ % & &. / (*) + + ˆŠˆŠˆŠ 02143 Ž Œ f n o ƒ x U prq st ]_^`_acbd l_m }_~ gih _ jck u8vw y_z{ γ VXWZY\[ ˆ ª «ª ± ²³ µ ¹ º»½¼ š œ ž Ÿ2 Searches for excited leptons in composite models and a SUSY breaking model with gravitino ¾ as LSP at LEP II. ÀÂÁÃÀÂÄÆÅ ÇÉÈÊÇÉÈÌËÎÍÏÇÉÈ\ÇÎÐÌÇÉÈÑÅ ÇÓÒÔÐ ÀÂÁÃÀÕÄÖÅ ØÔÙÚ ØÌÙÚ ËÎÍÛ ØÌÙÚ ÐÝ ØÌÙÚ Å Ü Ò L = 102.4 / pb DATA = 343 L3 MC (νν γ) = 353.6 (350.8) Events / 2 GeV 50 (14 o <θ ß à γ <166o ) 0 0 0.5 1 Photon Energy / Ebeam
Discovery Power of Precision Photons Há â Searches with PWO ECAL by CMS at LHC ç 8000 600 Events/500 MeV for 100 fb 1 æ 7000 å 6000 ä 5000 ã 4000 Events/500 MeV for 100 fb 1 400 200 0 110 120 130 140 110 120 130 140 a) m γγ (GeV) b) m γγ (GeV)
Higgs Searches by L3 at LEP II The Higgs background is suppressed by b-tagging and neural network analysis. Kinetic constraints improve mass resolution to è 3% for 87 GeV Higgs. éìêëéôì á íïîcðûñòíóîûá ôöõôø úùüûýðþîûá ÿ ÿõ Events/0.6 10 2 1 a) L3 Data HZ qqqq BG Events/0.05 10 2 1 b) L3 10-2 0 5 10 10-2 0 0.25 0.5 0.75 1 Events/2.5 GeV 10 1 10-1 B tag c) L3 Events/0.05 10 3 10 10-1 NN out d) L3 60 80 M rec H (GeV) 0 0.25 0.5 0.75 1 P M
What Can Crystal Calorimetry Offer? Good electromagnetic energy resolution because of total absorption: 0.6% is achievable for isolated e or,. Good position resolution because of its fine segmentation: 0.3 mm is achievable for cell size and Molière radius of 2 cm, mm. Good photon angular resolution because of no ambiguity in primary event vertex in LC bunch length 0.2 mm. Good e and identification and reconstruction efficiency because of fine granularity and pointing geometry: e/ discrimination better than 10 ì is achievable for e ID efficiency of 95%. Good missing energy resolution together with HCAL because of hermeticity. Good jet energy resolution by using information from other detector components: L3 achieved 7% for hadronic Z decays. Can be rather compact by using heavy crystals of less than 1 cm radiation length (PbWO and PbF ).
KTeV CsI Calorimeter & Measured Resolution
Bhabha Electron Energy Resolution with L3 BGO 0.5% Calibration Achieved in situ with RFQ Contribution Radiative +Intrinsic Temperature Calibration Overall Barrel 0.8% 0.5% 0.5% 1.07% Endcaps 0.6% 0.5% 0.4% 0.88% Events / 0.0025 1000 500 0 10000 45.6 GeV Barrel σ = 1.06% Endcaps σ = 0.86% < E Beam < 94.3 GeV σ(e) / E (%) 4 3 2 1 Barrel Endcaps 0 0.9 1 1.1 BGO energy / Beam energy 0 10-1 1 10 10 2 Energy (GeV)
" % # RFQ Installation in L3 Experiment L3 8235 5425 4010! 2530 14 180 mm Magnet Yoke Coil Muon Chambers BGO TEC Muon Filter % Hadron Calorimeter Barrel Support Tube Forward-Backward e e- Muon Chambers + HC1 HC3 HC2 Luminosity Monitor SMD RFQ $ y863col
& ' Improvement of L3 Jet Mass Resolution Using Information from other Detector Components 20000 18000 16000 14000 L3 Data 2 Jet Events σ(e Jet ) about 6.3 GeV (was 9.3 GeV) new algorithm old algorithm Events / GeV 12000 10000 8000 6000 4000 2000 0 20 40 60 80 100 120 140 Visible Energy [ GeV ]
( )*( ),+ CsI(Tl) ECAL and Resolution -10. All σ/e (%) / -1 Intrinsic Noise - -1 10 10-2 10-1 1 Energy (GeV)
CMS PbWO0 ECAL and Resolution 10 σ/e[%] 1 All Intrinsic Photo 1 0.1 Noise 1 10 100 1000 E[GeV]
Q O Crystal Position Resolution mm for R2436587:9<;=9 = 2 cm JEKBL GEHBI CEDBF >@?BA MENBMPO R@S TBU V@WEXBW Y[ZE\B] ^[_@_E`B_
Possible Choices of Crystal Technology Oxides: BGO is a mature and dense crystal (a = 7.13 g/cc, X = î 1.12 cm, R2b365c7ed 9P;=9 = 2.3 cm), but has a slow scintillation (300 ns) and not cost effective ($7/cc) due to expensive raw material (GeO ). PbWO is a mature and dense crystal (a = 8.28 g/cc, X = 0.89 cm, R2436587ed 9<;=9 = 2.0 cm). It is a fast and cost î effective crystal ($2.5/cc). Its low light yield is overcome by using Si avalanche photodiode. 0 gfh ij klmfn has been achieved with 25 mm APD readout in beam test. It is possible to develop a brighter PbWO crystal. Halides: CsI is a mature and cost effective crystal ($2/cc), but has low density (a = 4.5 g/cc, X = 1.85 cm, î R2b36587ed 9<;=9 = 3.5 cm). In addition, CsI(Tl or Na) is too slow ( è 1 o s) and CsI is less bright. PbF is a mature and dense crystal (a = 7.77 g/cc, X î = 0.93 cm, R2436587ed 9p;=9 = 2.1 cm). It is also cost effective (less than PbWO ). However, it is not yet a scintillator, but being used as a Čerenkov radiator. A scintillating PbF crystal may be developed by selected doping.
u u r õ CMS PbWO0 Energy Resolution in Beam Test Stochastic & Constant Terms q r st lmfn = 4.1% v 1.7 p.e./mev in 25 mm APD. CMS ECAL TDR uses 50 mm APD w = 2.9%. s õ of light response uniformity. = 0.37% v a better understanding of the consequence õ r
u Effect of Light Response Uniformity D. Graham & C. Seez, CMS Note 1996-002 Minimize contributions to the constant term of energy resolution, caused by light response non-uniformity.
0 q CMS PbWO0 ECAL Beam Test Resolution of 280 GeV Electrons xy{zn }~ mfn E l
PbWO0 Scintillation Light Output Measured with R2059 PMT Typical Full Size mf ƒ i l:i PWO 20 ˆ PWO F+S Light Output (p.e./mev) 15 10 5 ˆ PWO F 0 0 1000 2000 Time (ns) 3000 4000
PbWOŠ Scintillation Light Output fž f fž Œ PWO Size lœ 56 p.e./mev Measured with with R2059 PMT 80 SIC-S025 70 Light Output (p.e./mev) 60 50 40 30 20 10 0 Gate (ns): 50 100 200 1000 2000 10.2 14.8 22.3 49.2 55.4 10.0 14.4 21.9 48.7 red - as received 0 1000 2000 3000 4000 Time (ns) 55.2 green - tested before sent to Woody
Status of PbF Crystal as a Scintillator PbF has been studied in details as a Čerenkov material by D. Anderson and C. Woody et al., NIM A290 (1990) 385 and IEEE Trans. Nucl. Sci. NS-40 (1993) 546. Attempt has been made to produce scintillating PbF through phase transition (cubic to orthorhomic). Positive result reported by N. Klassen et al. in Crystal 2000 (1992) 587 does not agree with observations by S. Derenzo et al. IEEE Trans. Nucl.Sci. NS-37 (1990) 206 and D. Anderson et al. NIM A342 (1994) 473. Observation of fast scintillation in PbF (Gd) and PbF (Eu) was reported by D. Shen et al. (SIC) Jour. Inor. Mater. Vol 101 (1995) 11. The scintillation emission of PbF (Gd) was confirmed by C. Woody et al. in Delft Conference (1995), and 6.5 p.e./mev was observed for a PbF (Gd) sample of Œm lœ cm from SIC by using R2059 PMT. About 1,000 PbF crystals of lœ:š cm (a total of 0.167 m ) are being produced by SIC in 1998 for an experiment at Mainzer Microtron, Germany. They are used as Čerenkov radiator.
X-ray Excited Emission Spectra of PbF (Gd) D. Shen et al., Jour. Inor. Mater. Vol 101 (1995) 11.
X-ray Excited Emission Spectra of PbF (Eu) D. Shen et al., Jour. Inor. Mater. Vol 101 (1995) 11.
œ -ray Excited Emission Spectra of PbF (Gd) C. Woody et al., Delft Conference (1995)
PbF (Gd) ( Ÿž ž ž cm) Pulse Height Measured at AGS with 1 GeV/c MIPS by C. Woody et al. 6.5 p.e./mev Observed by R2059 PMT
Longitudinal Transmittance of PbF Measured with Hitachi U-3210 Photospectrometer n lœ š cm Sample from SIC 100 PbF 2 SIC-1 80 Transmittance (%) 60 40 20 0 200 300 ª 400 «500 600 700 Wavelength (nm) 800
Radiation Damage (10 krad) and Annealing lœ:š cm PbF Sample from SIC Measured by F. Maas
Summary To maximize physics reach, calorimetry for LC should have good measurement on electrons, photons and jets. A crystal calorimeter provides the best achievable resolutions for electrons and photons, a good missing energy resolution and an adequate jet resolution. Recently developed low cost, heavy crystals offers a cost effective crystal calorimeter solution. Feasible crystal technologies: A PbWOŠ calorimeter; A PbF calorimeter following successful R&D.