SuperNEMO Simulations Darren Price University of Manchester July, 2005

SuperNEMO Simulations Darren Price NEMO Collaboration Meeting - July 2005 Simulation details - geometry n Mylar-wrapped scintillators on 4 sides of detector: –Main calorimeters 2x250x360cm –Top and bottom calorimeters 20x250x2cm Use foil ( 82 Se) of width 250cm, height 275cm, thickness ~35  m –Foil 50cm from main scintillator, touching top and bottom scintillators n Wiring in tracking volume going from top to bottom in 3 bands (as in NEMO3) –One band of wires close to scintillator, band near middle of tracking and a band near the foil –Geiger cell dimensions used from NEMO3

SuperNEMO Simulations Darren Price NEMO Collaboration Meeting - July 2005 Simulation details - cuts n We require two hits in the calorimeter to accept an event, both of which must come from electrons created at the primary vertex n Once backscattered, electron is ignored, so cannot contribute to hit distribution, acceptance etc. n Require E min >0.1MeV for each electron to accept event n Need electrons to pass through at least 9 unique Geiger cells to count as a possible hit in calorimeter

SuperNEMO Simulations Darren Price NEMO Collaboration Meeting - July 2005 Simulation details - acceptance n Acceptance ratio for 0vbb varies between 50% and 20% n Plot of acceptance ratio with relation to foil vertex creation to the right n Currently working on acceptances with relation to energy cut and number of Geiger hits required foil centre

SuperNEMO Simulations Darren Price NEMO Collaboration Meeting - July 2005 Calorimeter – energy plots (8% res.) n Sum of two electron energies at scintillator (MeV) using a Gaussian smearing function corresponding to an 8% energy resolution at 1MeV (  )

SuperNEMO Simulations Darren Price NEMO Collaboration Meeting - July 2005 Calorimeter – energy plots (8% res.) n Sum of two electron energies at scintillator (MeV) using a Gaussian smearing function corresponding to an 8% energy resolution at 1MeV (2  )

SuperNEMO Simulations Darren Price NEMO Collaboration Meeting - July 2005 Calorimeter – energy plots (8% res.) n Sum of two electron energies at scintillator (MeV) using a Gaussian smearing function corresponding to an 8% energy resolution at 1MeV for neutrinoless double beta decay with Majoron emission (SI=1)

SuperNEMO Simulations Darren Price NEMO Collaboration Meeting - July 2005 Calorimeter - backscattering n Backscattered electrons from the (Bicron) scintillators have the following energy distribution n Only electrons backscattering for the first time are recorded (multiple backscatters not included in this plot) n Backscattering ratio is ~12.4% n Mean backscattered electron energy 680keV n Other materials also studied

SuperNEMO Simulations Darren Price NEMO Collaboration Meeting - July 2005 Tracking – Geiger cells n Wires added to the simulation –simulated octagonal cell wiring of NEMO3 with central anode wire surrounded by 8 other wires –low stepsize volume defined around each Geiger cell optimised for speed of calculation and fidelity of Geiger hit simulation n Modular design of the tracking/wire volumes had to be implemented to reduce the processing time for GEANT to search through many volumes n Added a random generator to simulate Geiger cell efficiency (96%) n Added code to ensure Geiger cell hits were unique (in case of backscattering etc.)

SuperNEMO Simulations Darren Price NEMO Collaboration Meeting - July 2005 Tracking – Geiger hit distributions n SuperNEMO simulation (LEFT) shows good agreement with NEMO3 data (RIGHT) NEMO 3 DATA Certain geometrical differences in NEMO3 slightly affect comparison

SuperNEMO Simulations Darren Price NEMO Collaboration Meeting - July 2005 Limit program - details n Using a limit program (MClimit) (NIM.A434, p , 1999) created by Tom Junk (University of Illinois) I ran an analysis on data generated from my simulation –Input spectra of signal + background –Get 90% confidence limits on effective neutrino mass, half-life. –Program allows inclusion of systematic uncertainties and uses shape information n Program takes multi-variable data to calculate limit – used: –Energy spectrum –Separation angle of the two generated electrons n Calculated the limit for 500kg.yrs

SuperNEMO Simulations Darren Price NEMO Collaboration Meeting - July 2005 Limit program - results n Using a 2-channel analysis of energy and angular distributions did not affect outcome (angular distribution below left) n Signal / background for angular distribution almost constant at 1 – so no real benefit – (s/b plot below right) signal/background (angular distribution) Angular distribution Blue = 2vbb Green = 0vbb+2vbb E cut >2.73MeV

SuperNEMO Simulations Darren Price NEMO Collaboration Meeting - July 2005 Limit program - results n Energy cut optimised using MClimit program n Shape information was used n Using nuclear matrix element |M| = 0.05 in analysis Optimum energy cut found to be E > 2.73MeV. Above is energy spectrum studied, to left is cut region. Blue = 2vbb Green = 0vbb+2vbb Result: n 90 =41, 6.01E+26

SuperNEMO Simulations Darren Price NEMO Collaboration Meeting - July 2005 Current work n Acceptance studies varying Geiger cell hit requirements, foil dimensions, energy cuts n Studies of wire diameter on electron energy loss Working on limit calculation for Majoron emission process (0  0 ) n Studies of energy resolution against effective mass limit n Thesis completion: 09/2005

SuperNEMO Simulations Darren Price University of Manchester July, 2005