1. The Shashlik Option for CMS B. Cox University of Virginia On behalf of: Baylor, Boston U, UC Davis, Caltech, CERN, ETH Zurich, Fairfield, Fermilab, Florida State, INFN (Milano-Bicocca, Roma1, Torino, Trieste), IHEP(Beijing), IHEP(Protvino), INP (Minsk, Moscow, Tashkent), Iowa, JINR Dubna, Kansas State, KIPT Kharkov, ISMA Kharkov, Maryland, MEPHI Moscow, NCPHEP Minsk, Northeastern, Notre Dame, Princeton, Rochester, Saclay, Saha Institute of Nuclear Phys., SINP Kolkata Institute, Texas Tech, TIFR Mumbai Institute, Virginia The Shashlik Collaboration B. Cox 8.4.16 1

2. 2 The Need for new CMS Endcaps It became obvious (due to the work of the CMS FCAL group, predecessor of the Shashlik group) in the time period 2010-2012 that the PbWO 4 endcaps would not survive to the stated goal of an integrated luminosity of 3000 fb -1 for the Phase II operation of the CMS detector in the decade of the 2020’s. The left hand plot shows the actual experience to date of the endcap light loss and the right hand plot has a simulation of the loss of Higgs  mass resolution (  ) as a function of eta and integrated luminosity.

3. B. Cox 8.4.16 3 The CMS FCAL group, after they determined that the PbWO 4 endcaps would not survive to 3000 fb -1 was charged with developing a endcap solution that would survive Phase II and, in addition, do as well or better for photon (and diphoton) resolution as the undamaged PbWO 4 electromagnetic endcap. do no worse than the present hadronic HCAL endcap on hadrons. Starting with this charge, three different options were investigated in a “downselect” process which resulted in two options selected for a final downselect: The Shashlik option (light based option) The HGC option ( electrical based option) This talk will describe the Shashlik Option Charge to the CMS FCAL Group (circa 2010)

4. B. Cox 8.4.16 4 Requirements imposed by the Charge on the endcap calorimetry Radiation hardness of all components of the calorimeter to integrated particle fluxes of a few X 10 15 /cm 2 Detector speed (fast scintillation of detector material and waveshifters) Ability to deal with pileup (minimize shower size with high density of detector material) Sufficient light light output to minimize stochastic contribution to resolution Avoid major issues that would lead to systematic contributions to the constant term; maintain its level to 1% or less.

5. The solution: the Shashlik Option: An Optical Calorimeter Radiation hardness 1.Use of dense materials 2.Small Molière Radius 3.Rad-hard materials 4.Short optical paths 5.Rad-resistant, small pixel photosensor B. Cox 8.4.16 5 LYSO(Ce) – High Brightness – Slowly degrades with dose – Blue/Violet emission WLS Capillaries – Liquid cores accommodate various WLS materials – Spectral matching straightforward – Sealed and Replaceable Photosensors – GaInP if proximate position – SiPM, small pix, cooled in a more remote location Shashlik style module configuration Transverse size of modules ~ ½ Swiss Franc Technologies chosen

6. The Shashlik Option as proposed for CMS Endcap Region Elevation viewView from the IP B. Cox 8.4.16 6 ~30,500 LYSO/W modules per endcap

7. Expected Shashlik EM Energy Resolution from GEANT4 + SLitrani B. Cox 8.4.16 7 As a function of eta the LYSO/W Shashlik has excellent photon resolution and is relatively invulnerable to radiation damage A series of tests at CERN in the H4 electron beam undertaken in 2014-16 to validate the resolution expectations

8. Shashlik 4x4 H4 Beam Test June 2016 (a complete test of the actual Shashlik modules) B. Cox 8.4.16 8 W/LYSO Shashlik Prototype of 16 modules: 28 W plates 2.5mm thick 29 LYSO Plates 1.5mm thick 64 WLS Capillaries: 1mm dia, DSB1 WLS Monitoring Fiber 0.9mm dia Holes drilled in LYSO Plates/No polishing Readout SiPM (10μm pixels, adjustable PDE = 7-25%) Fermilab PADE Boards (Preamp/Digitizer) Total 64 channels 10 million electrons accumulated At 20, 50, 100, 150, 200 GeV in the CERN H4 test beam BEAM

9. Basic Capillary Structure See poster on capillaries August 6, 18:00-20:00, Riverwalk A/B (http://indico.cern.ch/event/432527/contributions/1072109/http://indico.cern.ch/event/432527/contributions/1072109/ B. Cox 8.4.16 Core Blocking Thermal Expansion Reservoir Diffusive Reflector (DR) Surface Coating just before the Reservoir 180 mm Readout End Rad Hard Quartz (Polymicro QA): OD:ID = 1mm:0.4mm 9 Photons wavelength shifted from 425 nm to 550 nm in DSB1 core and transported in the rad had quartz outer cylinder to the SIPMs. No photon travels far in rad vulnerable materials

10. GaInPSmall Pixel SiPM B. Cox 8.4.16 10 Photosensor Choices Pixels: 5, 7.5, 10, 12um Operate cooled (down to -30c) to increase rad hardness Nearby or remote placement Experience with SiPM and multiple vendors Vendors: FBK, HPK… Pixels: 5um, 10um Can operate at ambient temperature because of good rad hardness Radiation hard due to large band gap Can be placed at the LYSO module Vendor: LightSpin 4x4 mm 2 GaInP light sensor 10 arrays of 0.5x1.5 mm2 2360 25µm pixels GaInP

11. Preliminary Resolutions from the October, 2014 and June, 2016 200 GeV H4 Electron Beam Tests B. Cox 8.4.16 11 Capillary resolutions are to be considered as preliminary and upper limits but even so are equivalent to Y11 fiber resolutions. Further Analysis in Progress.

12. Radiation Study: Irradiation Study at LANL of a LFS(LYSO)/W/Capillary Shashlik Module B. Cox 8.4.16 12

13. Shashlik Time Resolution with SiPM W/LYSO/DSB1 WLS B. Cox 8.4.16 13 Timing resolution improves with faster rise time. Achieving around 60ps for single capillary / SiPM (similar to Y11). Combined performance < 50ps for a single Shashlik cell. Further studies needed to understand if other limiting factors emerge. Dots: DSB1 fiber WLS Squares: Capillaries with DSB1 WLS

14. Future radiation testing upcoming to further quantify radiation hardness of key elements of the Shashlik technology Specific aspects of the R&D are potentially applicable to CMS Phase II upgrade and s other experiments Small pixel SiPM and GaInP photosensors WLS and Scintillator R&D Fast timing capability with LYSO and DSB1 We will present future results obtained to the broader scientific community (at CPAD, IEEE/NSS, APS) in the next several months. Papers are in preparation B. Cox 8.4.16 14 Summary Conclusion: The Shashlik was a viable option for CMS endcap calorimetry and is interesting for other experiments

15. BACK UP B. Cox 8.4.16 15

16. Radiation Studies: LYSO(Ce) Crystal Plates B. Cox 8.4.16 16 LYSO characteristics Bright (200 times PbWO 4 ) Decay time (40ns) Radiation damage to LYSO does not recover, leading to a stable calorimeter with slow degradation. Gamma and proton induced absorption coefficient is about 3m -1 for a dose of 150Mrad or 3 x 10 14 p/cm 2. This leads to a robust calorimeter with a few percent light output loss at HL-LHC.

17. Radiation Induced Absorption in LYSO B. Cox 8.4.16 17

18. Radiation Studies II: Light Collection losses due to radiation for a Capillary (425 nm light shifted to 500nm by DSB1 waveshifter) B. Cox 8.4.16 Relative Light Yield 0 0.2 0.4 0.6 0.8 Distance from LED to Photosensor (mm) 0 20 40 60 80 100 120 140 50Mrad/0Mrad 100Mrad/0Mrad 150Mrad/0Mrad 200Mrad/0Mrad 18 Good Longitudinal uniformity

19. Shashlik 4x4 H4 Beam Test (2014-2015) B. Cox 8.4.16 19 W/LYSO Shashlik Prototype of 16 modules: 28 W plates 2.5mm thick 29 LYSO Plates 1.5mm thick WLS Fibers: Kuraray 1.2mm dia, Y11 Monitoring Fiber 0.9mm dia Holes drilled in LYSO Plates/No polishing Readout both Upstream and Downstream SiPM (15μm pixels, PDE = 20-25%) Fermilab PADE Boards (Preamp and Digitizer) Total 128 channels