Non-Prompt Tracks with SiD BeamCal Radiation Damage Studies (Proposal) Two R&D Topics Non-Prompt Tracks with SiD BeamCal Radiation Damage Studies (Proposal) SiD Collaboration Workshop November 15-17 2010

Non-Prompt Tracking with the SiD Explore performance via explicit signature: Metastable stau NLSP (Gauge-Mediated SUSY)

Reconstructing Metastable Staus w/ SiD Gauge-Mediated SUSY Large tract of parameters space as stau NLSP Metastable (cstau ~ centimeters) is in cosmologically preferred region Process is with

Reconstructing Metastable Staus w/ SiD Start with: 5+1 layers for inside track 4 layers for outside track  Restricted range in rdecay for now; will expand soon

Measuring Staus with the SID Stau sample: 11.1 fb-1 of e+e- stau pairs with mstau = 75 GeV Ecm = 500;  = 90 fb c = 23 cm Background sample: 5.3 fb-1 combined SM background

Reconstructing Metastable Staus w/ SiD Focus initially on rdecay = 22-47 cm… Reconstruct decays by requiring:     - Outer hit of primary track on first tracker layer     - Inner hit of non-prompt track on second tracking layer    - Both tracks be on the same side of the Barrel (in z)     - The sign of the track curvatures match     - Non-prompt track curvature larger than the primary     - Tracks have a geometric intersection in the x-y plane Of 294 staus with 22<rdec<27 and |cos| < 0.5, 239 staus are reconstructed, of which 232 truth-match

Stau Reconstruction Efficiency Truth-Matched Staus

Signal to Background for 10 fb-1 Truth-matched stau: 210 Background kinks: 1338 Perhaps slight preference for background kinks to show up at material layers at 22 and 47 cm 47cm 22cm

Signal to Background (10 fb-1) Curvature ratio Kink angle

Signal to Background (10 fb-1) pT of prompt track #Tracks/event Good separation between signal and background for #tracks/event and track pt

Extend Region of Search: First Look Require prompt track end on VTX L5 or Tracker L1 Require non-prompt track start on Tracker L1 or L2 [L2 only for b)]

Stau Reconstruction Efficiency Truth-Matched Staus Tracker L1

S/B; Extended Region (10 fb-1) pT of prompt track Kink Radius Separation can still be made, but distinction between signal and background in prompt track pt somewhat degraded by reduced lever arm

Plans for Radiation Damage Studies for Si Diode Sensors Subject to 1 GRaD Doses CERN Linear Collider Workshop October 18-22 2010

But: Are electrons the entire picture? G.P. Summers et al., IEEE Trans Nucl Sci 40, 1372 (1993) NIEL e- Energy 2x10-2 0.5 MeV 5x10-2 2 MeV 1x10-1 10 MeV 2x10-1 200 MeV Damage coefficients less for p-type for Ee- < ~1GeV (two groups); note critical energy in W is ~10 MeV But: Are electrons the entire picture? 15 15

Hadronic Processes in EM Showers There seem to be three main processes for generating hadrons in EM showers (all induced by photons): Nuclear (“giant dipole”) resonances Resonance at 10-20 MeV (~Ecritical) Photoproduction Threshold seems to be about 200 MeV Nuclear Compton scattering Threshold at about 10 MeV;  resonance at 340 MeV  Flux through silicon sensor should be ~10 MeV e/, but also must appropriately represent hadronic component 16 16

Rates (Current) and Energy Basic Idea: Direct electron beam of moderate energy on Tungsten radiator; insert silicon sensor at shower max For Si, 1 GRad is about 3 x 1016/cm2, or about 5 mili-Coulomb/cm2 Reasonably intense moderate-energy electron or photon beam necessary 17 17

5.5 GeV Electrons After 18mm Tungsten Block Not amenable for uniform illumination of detector. Instead: split 18mm W between “pre” and “post” radiator separated by large distance Caution: nuclear production is ~isotropic  must happen dominantly in “post” radiator! Boundary of 1cm detector Fluence (particles per cm2) Radius (cm) 18 18

5.5 GeV Shower Profile e+e- (x10) All  E > 100 MeV (x20) “Pre” “Post” e+e- (x10) All  Remember: nuclear component is from photons in 10-500 MeV range. Fluence (particles per cm2) E > 100 MeV (x20) E > 10 MeV (x2) Radius (cm) 19 19

Proposed split radiator configuration 5mm Tungsten “pre” 13mm Tungsten “post” Separated by 1m Fluence (particles per cm2) 1.0 2.0 3.0 20 Radius (cm) 20

Rastering Need uniform illumination over 0.25x0.75 cm region (active area of SCIPP’s charge collection measurement apparatus). Raster in 0.05cm steps over 0.6x1.5 cm, assuming fluence profile on prior slide (see next slide for result) Exposure rate: e.g. 10 GRad at 50 nA 5.5 GeV e-  ~ 30 Hours

Irradiation Plan Use existing Micron sensors from ATLAS R&D n-type and p-type Standard float-zone and Magentic Czochralski Runs of up to 1 GRad for each sample Runs with samples far from radiator (no hadronic effects) Total integrated dose of ~10 Grad Will assess the bulk damage effects and charge collection efficiency degradation. Sensors Sensor + FE ASIC DAQ FPGA with Ethernet 22 22

Wrap-Up Non-Prompt Tracks with SiD: Reconstructing clean metastable stau signature between first and second tracking layer with high efficiency. Backgrounds have low primary track momentum. Region between VTX and tracking L1 looks promising; needs more work. Between L2 and L3 requires dedicated tracking algorithm (exploring). Radiation Damage for ~1 GRad EM Showers Some evidence that p-bulk sensors will be most robust. Need to worry about nuclear effects. Looking for facility (SLAC ESA beam would require 2-4 weeks of exposure when available)

NIEL (Non-Ionizing Energy Loss) Conventional wisdom: Damage proportional to Non- Ionizing Energy Loss (NIEL) of traversing particle NIEL can be calculated (e.g. G.P. Summers et al., IEEE Trans Nucl Sci 40, 1372 [1993]) At EcTungsten ~ 10 MeV, NIEL is 80 times worse for protons than electrons and NIEL scaling may break down (even less damage from electrons/positrons) NIEL rises quickly with decreasing (proton) energy, and fragments would likely be low energy  Might small hadronic fractions dominate damage? 24 24

BeamCal Incident Energy Distribution 2 4 6 8 10 e+/e- ENERGY (GEV) 25 25

Wrap-up Worth exploring Si sensors (n-type, Czochralski?) Need to be conscious of possible hadronic content of EM showers Energy of e- beam not critical, but intensity is; for one week run require Ebeam(GeV) x Ibeam(nA) > 50 SLAC: Summer-fall 2011 ESA test beam with Ebeam(GeV) x Ibeam(nA)  17 – is it feasible to wait for this? 26 26

Shower Max Results Photons with E > 100 MeV per electron, x 100 Photons with E > 10 MeV per electron, x10 Photons per electron Electrons, per GeV incident energy 1.0 2.0 3.0 27  Photon production ~independent of incident energy! 27

Proposal: JLAB Hall B Beam Dump (Plan to run 0 Proposal: JLAB Hall B Beam Dump (Plan to run 0.05 A through next May)  Total power in beam ~250W. Oops – too much background for Hall B! Look elsewhere…

Fluence (e- and e+ per cm2) per incident 5.5 GeV electron (5cm pre-radiator 13 cm post-radiator with 1m separation) mm from center 1 2 3 4 13.0 12.8 11.8 9.9 8.2 13.3 12.9 12.0 13.1 12.6 11.7 5 12.3 6 11.6 10.7 7 10.4 8 8.6 8.0 6.4 Center of irradiated area ¼ of area to be measured ¼ of rastoring area (0.5mm steps)