New nEDM Sensitivity Calculation T. Langford B. Beise University of Maryland 7/3/2008 Simulation Teleconference Starting Points: Work by V. Cianciolo, Feb 2006 Collaboration Meeting Section V.H of 2002 Pre-Proposal Chibane, etal, Meas. Sci. Tech. 6 (1995) 1671 Internal report LAUR , Van Cleve & Cooper

Rate Function from Pre-Proposal τ β and τ 3 are the decay time of the neutron and the decay time due to n + 3 He capture N is the total number of events, N =.86PVτ where τ is the average decay time, P is the UCN Production Rate and V is the volume (Pre- Proposal p. 141) Γ Ave is the average of all three decay rates; beta decay, 3 He capture and cell loss P 3 and P n are the initial polarization percentages of the 3 He and UCN Γ P is the depolarization rate of the 3 He

Where are we with Parameter R&D? Solid Parameters – Gamma P – P3 Need better data – Cell loss rate ★ – E Field Gradient – UCN Production Rate ★ – Initial Polarization of UCN, 3He – Shape of Background, currently only have Beta decay – ?

Basics of Our Code We took the code Vince Cianciolo wrote and replaced the rate function and parameter declaration (His presentation)presentation Vince’s rate function did not match that of the Pre-proposal, so we replaced it with eq. V.H.1 We then use his Minuit fitting routine to extract both the phase of the oscillation and the dfEDM

Example Run of the EDM Generation Note: The initial rate is higher than Vince’s by a factor of 4 due our rate function

Reproduction of Pre-Proposal Δf This takes the same approximations and assumptions as on pg. 141 in Pre-Proposal where a Sigma = 2.6 μHz was reported

Main Differences between Pre-Proposal and Current Specs The volume has changed from 4000cc to 2300cc (from CDR pg. 81) UCN Production Rate changed from 1 UCN/cc/sec to.3 (Paul Hauffman) Cell loss time at 500s instead of 1000s (makes it the dominant term in the average decay rate) E field gradient of 40 kV/cm which changes dfEDM to 2.3 μHz from 2.9 μHz Used 95% polarization and concentration for 3 He since we do not know how they couple, see C. Swank’s notes from Duke meeting

Histogram of Current Spec Runs

Current Specification Run In order to pass into CD-2, we need to show an ability to reach a 90% CL of 2σ = 3 x e cm This corresponds to a σ mean = 5.8 x Hz Our histogram shows a Δf = Hz, knowing that the overall σ mean scales with we can calculate the total run time We then need 32,463 runs to meet the CD-2 level, which corresponds to 188 live days

Modeling PMTs We have begun work on modeling the Photo Multiplier Tubes in the system We generate random events in each of the PMTs and then look for coincidences between tubes This has not changed the outcome much yet, but is more closely related to the method of the experiment Waiting on data on PMTs from Tito’s group at Los Alamos

Modeling of Background In the first iteration of the code, the background was incorporated in the overall rate function This prohibits viewing the isolated background to study its shape and size The background is now separate and is randomly generated using the same method as the signal The signal and background are then merged and the analysis is done on the whole

What’s Next We have already started looking at different shapes of background and the effects on σ mean Search for the dominant parameters; where we get the most impact from improvement Continue to update parameters as R&D progresses Signal Identification? Comments?