Search for Extra Dimensions in diphotons at CMS

1. Search for Extra Dimensions in diphotons at CMS Duong Nguyen Brown University APS April Meeting Washington DC., Feb. 16, 2010

2. Outline • LHC (Large Hadron Collider) and CMS detector • ECAL first collision commissioning • Non-resonance search (Arkani-Hammed, Dimopolous and Dvali model) • Resonance search (Randall-Sundrum model)

3. CMS detector

4. CMS electromagnetic calorimeter (ECAL) 0.5 m 2.6 m 6.4 m Endcap Dee Barrel Super Module Pb-Si Preshower PbWO4 Light emission: 80% in 25 ns Radiation length: X0 = 0.89 cm Molière radius: RM = 2.10 cm Emission peak: 425nmGood radiation resistance to very high doses 22cm 24.7Xo 23cm 25.8Xo 23cm 25.8Xo 22cm 24.7Xo

5. Pi0 peak observation A photon is converted egamma900GeVapproval.ppt http://indicobeta.cern.ch/conferenceDisplay.py?confId=76852

6. Extra Dimensions

9. RS

10. Backup

11. Pi0 peak plenary_1612_updated http://indicobeta.cern.ch/materialDisplay.py?contribId=9&sessionId=2&materialId=slides&confId=76852

12. Check on Luminosity using p0 Rate of physics events proportional to number of reco’ed p0’s Steps: • p0’s yield extracted vs run • p0’s yield divided by efficiency (MC) and cross section (50mb) to extract integrated lumi • Measured lumi rescaled by: (Total p0 lumi) / (tot HF lumi) • Rescaled lumi plotted vs run number or vs HF lumi Useful to: • Check efficiency of ECAL and HLT filter • Cross-check lumi with HF

13. Check on Luminosity using p0 (II) p0 instantaneous luminosity vs lumi section L1Tech_HF rate vs time p0 lumi/HF lumi vs HF lumi normalized to unity

14. h Yield in ECAL Barrel plenary_1612_updated http://indicobeta.cern.ch/materialDisplay.py?contribId=9&sessionId=2&materialId=slides&confId=76852 MC DATA • Mass and width compatible with MC • h yield scale as expected (p0 candle) • N(h) / N(p0) = 0.020 ± 0.003 DATA • N(h) / N(p0) = 0.021 ± 0.003 MC

15. LHC SPS • Large Hadron Collider (LHC) • Nominal c.o.m energy: 14TeV • Nominal luminosity: 1034 cm-2s-1 • Collision rate: 40MHz • Number of bunches per ring: 2835 • Number of particles per bunch: 1011

16. Tapered crystals to provide off-pointing of ~ 3o from vertex Barrel crystals Pb/Si EndcapPreshower Endcap ‘Dee’ with ‘Supercrystals’ Barrel36 Supermodules (18 per half barrel)61200 crystalsTotal crystal mass 67.4t|| < 1.48  x  = 0.0175 x 0.0175 Endcaps4 Dees (2 per endcap)14648 crystals Total crystal mass 22.9t1.48< || < 3  x  = 0.01752↔ 0.052 Endcap PreshowerPb (2Xo,1Xo) / Si4 Dees (2 per endcap)4300 Si strips1.8mm x 63mm1.65< || < 2.6 ICHEP 2008 D J A Cockerill - RAL 16

17. 70% 425nm350nm 23cm 25.8Xo 22cm 24.7Xo 300nm 700nm Barrel crystal, tapered34 types, ~2.6x2.6 cm2 at rear Endcap crystal, tapered1 type, 3x3 cm2 at rear Emission spectrum (blue)and transmission curve Reasons for choice Homogeneous mediumFast light emission ~80% in 25 ns Short radiation length X0 = 0.89 cm Small Molière radius RM = 2.10 cm Emission peak 425nmReasonable radiation resistance to very high doses CaveatsLY temperature dependence -2.2%/OC Stabilise to  0.1OC Formation/decay of colour centres Need precise light monitoring system Low light yield (1.3% NaI) Need photodetectors with gain in magnetic field ICHEP 2008 D J A Cockerill - RAL 17