Use of the BeamCal to Constrain ILC IP Beam Parameter ECFA Linear Collider Workshop Palacio de la Magdalena Santander, Cantabria, Spain May 30 – June 5, 2016 Bruce Schumm UC Santa Cruz Institute for Particle Physics Don’t forget x,y recon results X2 background effect Description of algorithm Segmentation strategy study 1

Contributors Goal Luc D’Hauthuille, UCSC Undergraduate (thesis) Anne Schuetz, DESY Graduate Student Christopher Milke, UCSC Undergraduate With input from Glen White, Jan Strube, B.S. Goal Idea is to explore the sensitivity of various beamstrahlung observables, as reconstructed in the BeamCal, to variations in IP beam parameters. The sensitivity will be explored with various different BeamCal geometries.

IR Layout Low-Z Mask M1 Mask BeamCal L* 3 3 3

BeamCal Pixellation (Cartoon)

Of these, we believe the following can be reconstructed in the BeamCal: Total energy and its r, 1/r moment Mean depth of shower Thrust axis and value (relative to barycenter; could also use mode of distributions. What is wise choice though? Maybe just (0,0)?) Mean x and y positions Left-right, top-bottom, and diagonal asymmetries

BeamCal Face Geometry Options “plugged” Wedge cutout Circle cutout “wedge” cutout Plug Insert plug here “circle” cutout 6 6 6

IP Parameter Scenarios Thanks to Anne Schuetz, GuneaPig expert Relative to nominal: Increase beam envelop at origin (via -function), for electron and positron beam independently, by 10%, 20%, and 30% Move waist of electron and positron beam (independently) back by 100m, 200 m, 300 m. Change targeting angle of electron and positron beam (independently) by 5 mrad and 20 mrad (in retrospect, isn’t this a bit much?) Details at https://wikis.bris.ac.uk/display/sid/GuineaPig+simulations+for+BeamCal+study

First (Early) Results Luc has coded the following observables: Deposited energy, mean depth of shower, L/R and up/down asymmetries, thrust (relative to barycenter) value. He has taken eight beam crossings (working on larger sample soon!) and explored the following “trajectories”: Beam envelope for electrons Beam envelope for positrons Electron waist position Following are a core-dump of plots of these observables over those trajectories.

(Electrons and Positrons) Beam Envelope Scan (Electrons and Positrons)

Total Deposited Energy e+ and e- beam envelope scan

e+ and e- beam envelope scan Mean Depth e+ and e- beam envelope scan

e+ and e- beam envelope scan L/R Asymmetry e+ and e- beam envelope scan

e+ and e- beam envelope scan Up-Down Asymmetry e+ and e- beam envelope scan

e+ and e- beam envelope scan Thrust Value e+ and e- beam envelope scan

Waist Scan (Electrons Only)

Total Deposited Energy e- waist scan

Mean Depth e- waist scan

L/R Asymmetry e- waist scan

Up-Down Asymmetry e- waist scan

Thrust Value e- waist scan

Summary and Conclusions First look at BeamCal observables and IP parameter dependence Need to finish coding observables (thrust definition question) Need to increase statistics (~100 pulses generated; working on simulation) Need to develop some more interesting IP parameter variations (discussion!) Need to explore sensitivity to BeamCal geometry But this should be a good foot in the door for now…