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Magnetic field for “PANDA*” * P roton A symmetry in N eutron D ec A y

Magnetic field for “PANDA*” * P roton A symmetry in N eutron D ec A y. For the SNS-FnPB Magnet meeting Prepared by Tim Chupp. The proton Asymmetry. e. e. p. p. n. n. N +. N -. N + - N - N + + N -. Asymmetry: __________ = C P n A F (1-f) + A false.

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Magnetic field for “PANDA*” * P roton A symmetry in N eutron D ec A y

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  1. Magnetic field for “PANDA*” *Proton Asymmetryin Neutron DecAy For the SNS-FnPB Magnet meeting Prepared by Tim Chupp

  2. The proton Asymmetry e e p p n n N+ N- N+ - N- N+ + N- Asymmetry: __________ = C PnA F (1-f) + Afalse background spin flip efficacy analyzing power neutron polarization gA gV |l| 1+3| l |2 C = k(A+B) = 4k ________ l = ____ k=0.27484 Standard Model dW pe.pn meJpe pnpexpn _____________ = S(Ee)[1 + a ______ + b ___ + ___.(A____ +B____ +D _______ )] dEedWedWnEeEn Ee J Ee EnEeEn JTW-57

  3. C and l |l| 1+3| l |2 C = k(A+B) = 4k ________ sx x sl l PDG 2005 ___ ___ l -1.2695±0.0029 a -0.103±0.004 0.2688 A -0.1173±0.0013 0.2403 B +0.983 ±0.004 1.385 C +0.238 ±0.011* 1.430 D -0.0004±0.0006 f 180.06±0.0029 * Abele, 2005 dW pe.pn meJpe pnpexpn _____________ = S(Ee)[1 + a ______ + b ___ + ___.(A____ +B____ +D _______ )] dEedWedWnEeEn Ee J Ee EnEeEn JTW-57

  4. Rudimentary Layout By For adiabatic neutron spin transport Bx M2 M1 Neutron spins tranported Through detector polarizer analyzer Spin Flipper X N0(v) y neutrons P(v) TP(v) A(v) TA(v) R z Detector L Detector 2 Detector 1 Neutron beam Into page +30 kV V0 ~ ~ ~ Allows proton spectroscopy ~ Detailed design work needed. Uniform field B

  5. Neutron spin transported adiabatically from polarizer to analyzer (through detector) Uniform B in decay region: mitigates proton reflections from magnetic traps Proton orbit: d= 8 mm/B(T): 1-2T Needed (2 T for emiT proton segment Electrostatic proton energy resolution desired: requirements on B in proton drift region TBA Vacuum requirements: TBA General Design Issues Goal: sx/x ~ 10-3 or better

  6. Neutron Polarization and Polarimetry M2 M1 polarizer analyzer Spin Flipper X N0(v) neutrons P(v) TP(v) A(v) TA(v) R Detector RExp= S( + ) + D( - ) =N0T1T2TP [G0+DPR] G±=S±D M1= N0e1+B1 M2= N0T1T2TPTAe3 [ 1+PAR] +B2 P/A Pn (5Å) Tn P2T features PSM 99.x% 10% 0.1 fixed; limited l bite 3He (60%) 80% 30% 0.2 flip P3; P3 varies Flipper: Ru= 1 (unflipped); Rf=F≈-1 (flipped) (-0.999 for AFP) (M2u - M2f) (M2u + M2f) _________ ~ PA(1-F) (1-f2) BR (1% need to know to 0.1%)

  7. L Detector Detector 2 Detector 1 Neutron beam Into page +30 kV V0 ~ ~ ~ Allows proton spectroscopy ~ Detailed design work needed. Uniform field B Ideal: A1=A2=1, e1=e2=1, f1=f2=0 Proton detection: e.g. emiT2 • with adiabatic spin transport J||B • with adiabatic proton orbits, A=1 (scattering: resid. gas, baffles, etc.)

  8. Statistics rn ~ 103/cm3 We expect about 0.5 decays per pulse: about 2.5 million events per day. 0.1% precision requires < a few days NOT STATISTICS LIMITED Focus on systematics…

  9. Systematics N+ - N- N+ + N- __________ = C PnA F (1-f) + Afalse background spin flip efficacy analyzing power neutron polarization Need to know: neutron polarization analyzing power spin flip efficiency backgrounds spin independent spin dependent (false asymmetry) e.g. False asymmetry from electrons emited from n-decay (BR) - study of proton energy dependence Noise, gain shifts, etc. - flip 3He C is INDEPENDENT of Pn, xy, L, tof, 3He, B, BR, … statistical power

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