T-violating observables in neutron decay experimental opportunities - PowerPoint PPT Presentation

„ Theoretical issues and experimental opportunities in searches for time reversal invariance violation using neutrons ” , Dec. 6-8, 2018, Amherst MA T-violating observables in neutron decay – experimental opportunities Kazimierz Bodek Marian Smoluchowski Institute of Physics, Jagiellonian University, Krakow, Poland

2 07.12.2018 T-violating observables in neutron decay – experimental opportunities Outline  T-odd correlations in neutron  -decay  D- and R-correlations  Experiments in the past: emit, Trine and nTRV  emit+Trine+nTRV together (?)  BRAND  Potential benefits of BRAND  T-odd correlation in radiative neutron decay  Challenges and strategy  Conclusions

3 07.12.2018 T-violating observables in neutron decay – experimental opportunities TRV tests  True TRV tests require (i) reversal of motion and (ii) exchange of initial and final states t  -t (a) (b) Initial Final Initial Final Scattering, binary reaction: 3 1 1 3 2 4 4 2  In particle decay exchange of initial and final states is impossible Particle decay: 3 3 1 1 4 4  (a) ≠  (b)  If interaction violates TR symmetry:

4 07.12.2018 T-violating observables in neutron decay – experimental opportunities D - and R -correlations  In ordinary neutron decay, two observables are particularly interesting R  < J >/ J  ( p e  ) D  < J >/ J  ( p e  p  ) R D  D -correlation (C-odd, P-even, T-odd)        J d p p m p p p p   1           D     e e e e S E a b A B D   e   dE d d E E E J E E E E       e e e e e e  R -correlation (C-even, P-odd, T-odd)         σ p p σ p σ J J d m p p   1          σ R   e e e  e e e  S E b A G Q N R   e   dE d  E J E E J E E m E  e e e e e e e e e       σ J d m p p   1         σ R σ p   e  e e  S E b A N R ;    e e   dE d E J E E   e e e e e

5 07.12.2018 T-violating observables in neutron decay – experimental opportunities D -correlation J.D. Jackson et al., Phys. Rev. 106, 517 (1957); J.D. Jackson et al., Nucl. Phys. 4, 206 (1957); M.E. Ebel et al., Nucl. Phys. 4, 213 (1957)    For left-handed V-A interactions ( ), defining C C ' , C C ' V V A V  = C A / C V , neglecting terms quadratic in C S and C T , point charge, no recoil:       5 1.2 10 D D D D FSI T T        * * *   Im C C Im C C C ' C ' 1   V A  S T S T   D 2 T   2 2 2   1 3 C C   V V      * * ' m 1 C C ' C C     * *  T T S S  Re   2 *   p C C 1 3 e A V       1 C C ' C C '             * * S S T T D 2sin Im S T S T ; S , T T AV   2 C C 1 3 V A   VA D 0.435 sin AV T

6 07.12.2018 T-violating observables in neutron decay – experimental opportunities D -correlation, emit-II  emiT-II (NIST):  NG6 cold neutron beam Longitudinally polarized (~0.95) in the fiducial volume  Compact, symmetric setup with azimuthally alternating  electron- and proton-detectors Proton detectors segmented (4x4 cm 2 ) SBD, accelerating  potential ~25 kV

7 07.12.2018 T-violating observables in neutron decay – experimental opportunities D -correlation, emit-II  Acquired information  e-p coincidences, ToF Electron energy  (Accelerated) proton energy   Isolation of D using: Symmetry of detectors  Periodic neutron spin flip 

8 07.12.2018 T-violating observables in neutron decay – experimental opportunities

9 07.12.2018 T-violating observables in neutron decay – experimental opportunities D -correlation, emit-II  Result (68% C.L.) T. E. Chupp, R. L. Cooper, K. P. Coulter, S. J. Freedman, B. K. Fujikawa, A. Garcia, G. L. Jones, H. P. Mumm, J. S. Nico, A. K. Thompson, C. A. Trull, F. E. Wietfeldt, and J. F. Wilkerson, Phys. Rev. C 86 , 035505 (2012)

10 07.12.2018 T-violating observables in neutron decay – experimental opportunities curtesy of H.P. Mumm (  10 -4 ) Most of systematic effects were MC modelled

11 07.12.2018 T-violating observables in neutron decay – experimental opportunities emiT-II+NGC

12 07.12.2018 T-violating observables in neutron decay – experimental opportunities D -correlation, emit-III+NGC

13 07.12.2018 T-violating observables in neutron decay – experimental opportunities D -correlation, Trine T. Soldner, L. Beck, C. Plonka, K. Schreckenbach, O. Zimmer, Phys. Lett. B 581 (2004) 49  Trine (ILL):  PF1 cold neutron beam Longitudinally polarized (~0.97) in the fiducial volume  Compact setup with planar geometry  Electron- and proton-detectors in perpendicular planes   Proton detectors PIN diodes on ground potential Accelerating potential: 25 kV  MWPC for gamma suppression and selection of angular ranges 

14 07.12.2018 T-violating observables in neutron decay – experimental opportunities D -correlation, Trine T. Soldner, L. Beck, C. Plonka, K. Schreckenbach, O. Zimmer, Phys. Lett. B 581 (2004) 49  Excellent S/B ratio of 23  Systematic effects and corrections

15 07.12.2018 T-violating observables in neutron decay – experimental opportunities D -correlation with ep/n + MagSpec ? e.g. G. Konrad et al., J. Phys.: Conf. Series 340 (2012) 012048  ep/n-spectrometers adiabatically coupled to n-decay channel (PERC, ANNI)  Conserve particle energy and angular (polar) distributions  Reconstruct p e  p p using decay kinematics (?) R  B NoMoS  No definite plans yet (B. Maerkisch, TUM) X. Wang, G. Konrad, H. Abele, NIMA (2012) 254

16 07.12.2018 T-violating observables in neutron decay – experimental opportunities R -correlation    For left-handed V-A interactions ( ), defining C C ' , C C ' V V A V  = C A / C V , neglecting terms quadratic in C S and C T , point charge, no recoil:  m         4 9 10 R R R R A R FSI SM T T T p     e       * * * * * *   Im C C C ' C ' Im C C C ' C C C ' C C 1  T A T A  S A S A V T V T   R 4 2 T   2 2 2   1 3 C C   V V  m 1          Re 2 1 R   FSI   2 p 1 3 e            1 2   C C ' C C '         S S T T R Im S Im T ; S , T T   2   2 C C 1 3 1 3 V A          R 0.218 Im S 0.335 Im T T

17 07.12.2018 T-violating observables in neutron decay – experimental opportunities N -correlation J n P p N  N is C-even, P-even and T-even  e R p e p  m         2 N N N N A N 7.9 10 T SM T SM T E e m 1          N Re 2 1   SM   2 E 1 3 e            1 2   C C ' ' C C         S S T T N Re S Re T ; S , T T   2   2 C C 1 3 1 3 V A          N 0.218Re S 0.335Re T T

18 07.12.2018 T-violating observables in neutron decay – experimental opportunities Electron spin analysis  Mott scattering:  Analyzing power caused by spin-orbit force  Parity and time reversal conserving (electromagnetic process)  Sensitive exclusively to the transverse polarization

19 07.12.2018 T-violating observables in neutron decay – experimental opportunities nTRV@PSI – Mott polarimeter  Challenges:  Weak and diffuse decay source  Electron depolarization in multiple Coulomb scattering  Low energy electrons (<783 keV)  High background (n-capture) Pb-foil Pb-foil  Solutions:  Tracking of electrons in low- 50 cm mass, low- Z MWPCs  Identification of Mott- scattering vertex (“V - track”)  Frequent neutron spin flipping  “foil - in” and “foil - out” scintillator MWPC scintillator measurements

20 07.12.2018 T-violating observables in neutron decay – experimental opportunities Limits on S and T contributions A. Kozela, G. Ban, A. Bialek, K. Bodek, P. Gorel, K. Kirch, St. Kistryn, O. Naviliat-Cuncic, N. Severijns, E. Stephan, and J. Zejma, Phys. Rev. C 85, 045501 (2012).