An Exotic Photon Cloud Trigger for CMS

Conor Henderson (CERN)

Introduction

We propose a novel trigger to be sensitive to a new kind of beyond-Standard-Model physics: a 'photon cloud', consisting of ~ 200 GeV of transverse energy emitted through many soft photons (< ~1 GeV each). Such an exotic event could potentially be overlooked by conventional trigger configurations, since no individual detector region has particularly high activity. By considering a simple new variable, Sum-Et in the electromagnetic calorimeter, which is straight-forward to calculate in a high-level trigger, CMS could be sensitive to this photon-cloud scenario. Estimated rates for this trigger for the expected LHC early luminosity scenario show that the proposal is feasible.

Trigger Proposal

Propose two triggers:

HLT_EcalOnly_SumEt160

• seed from L1_ETT100
• make all ECAL rechits (not just regional)
• make EB-only calo towers
• make standard MET/SumEt object from the ECAL-only calo towers
• use standard SumEt filter on this ECAL-only MET/SumEt object

HLT_L1SumEt100

• simple prescaled pass-through of the L1_ETT100 seed
• set prescale to 100

Trigger Studies

HLT trigger rate and timing studies are presented in my TSG talk of 25 March 2010

Papers

• Contribution to the proceedings of the 2009 Les Houches Workshop on Beyond-Standard Model Physics
  • Chapter 15 of http://arxiv.org/abs/1005.1229
  • Local copy: ecal_sum_et_trigger_les_houches_v4.pdf

CMS Presentations

• Trigger Studies Group, 25 March 2010

• Exotica, 15 Dec 2009

• Trigger Studies Group, 14 Dec 2009

• Exotica, 4 Sept 2009 (Initial Proposal)

-- ConorHenderson - 22-Jun-2010