CP Violation in Positronium Decay The Pecking Order Lana Del Reyco Chelsea Neutron Joule Kadeem Nibbs

Purpose Standard Model predicts Charge-Parity (CP) symmetry (for the most part) CP violation necessary to explain matter- antimatter asymmetry in universe Observed in quark sector, not yet in lepton sector 7/25/20152

The Great White Buffalo (Positronium) Bound state of electron and positron (bound state of particle and antiparticle) Singlet (Para-)Triplet(Ortho-) 2 gamma ray decay3 gamma ray decay 125 picosecond lifetime140 nanosecond lifetime No CP observableCP Observable 7/25/20153

Detecting CP Violation Angular correlation between spin of ortho- positronium (o-Ps) and directions of emitted gamma rays Asymmetry between positive and negative values of sin2θcosφ θ φ k1k1 k2k2 S 7/25/20154

The APEX Array Source Holder Configuration NaI BarPMT 7/25/20155

Gamma Ray Detection Gamma ray striking detector causes cascade of scintillation light Light creates current in PMT PMT base creates voltage proportional to current Digitizer records voltages in memory buffer – SIS Ms/s 7/25/20156

Event Reconstruction One way to find position: Light Attenuation (thank you Stephen Daigle) A1A1 A2A2 x0x0 Charge Amplitude from PMT1 Charge Amplitude from PMT2 7/25/20157

Possible Issue This can happen: – Gamma ray deposited in inconvenient place – Scintillation light reflected or absorbed by frame of PMT – Skewed ratio of signal strength from each PMT – Bad position reconstruction, false asymmetry measurement 7/25/20158

Solution: Additional Position Info Use time of light entering PMTs x t 1 is time light enters PMT 1 t 2 is time light enters PMT 2 Index of refraction of NaI 7/25/20159

My Job Extract timing information from waveform (from 22 Na source) Threshold Peak Half-Peak 7/25/201510

My Job (Cont.) Blown up portion of waveform from half- peak to baseline Detection Time Baseline Least Squares Line 7/25/201511

Results 7/25/ Number of Hits Detection Time (Digitizer Cycles)

Future Work Use calibrated delay line to test accuracy of my timing reconstruction algorithm Test validity of location reconstruction – Is it close to the light attenuation method in most cases? – Can the two results check each other? 7/25/201513

Acknowledgements Reyco Henning Mark Howe Chelsea Bartram Joule Othman Stephen Daigle Chiara Salemi 7/25/201514

Energy Spectra: Na22 Source 7/25/201515