The LPCTrap experiment: measurement of the β-ν angular correlation in 6He+ decay using a transparent Paul trap

Abstract

The LPCTrap experiment is devoted to the precise measurement of the β-ν angular correlation parameter, a βν , in the pure Gamow-Teller decay of 6 He + . This experiment is motivated by the search of the presence of tensor type contributions in the weak interaction. The radioactive source is confined in a transparent Paul trap installed at LIRAT, the low energy beam line of the SPIRAL facility. The β-ν correlation is studied by measuring the time of flight of the recoil ions detected in coincidence with the β particles. During the last experiment, a total of 4 × 10 6 coincidence events have been recorded which would enable to determine the coefficient with a statistical uncertainty of 0.5%. The status of the analysis is presented in this contribution. Keywords Ion trapping · Precision measurement · β-ν correlation MotivationIn the Standard Model (SM), the β decay is mediated by the W boson, giving rise to a pure V-A Lorentz current and excluding other Lorentz invariant contributions, i.e. tensor (T), scalar (S) and pseudo-scalar (P) [1]. Precision measurements of correlation coefficients in nuclear β decay enable to probe the presence of such nonstandard (exotic) contributions. For allowed transitions, the differential decay rate has the form:where W 0 (E) is a phase space term; m, v and E are respectively the mass, the velocity and the energy of the β particle; θ is the angle between the two leptons momenta and

New physics searches in nuclear and neutron β decay

“…Analysis of a first measurement with 6 He [302,322], with a total of about 10 5 β-recoil coincidence events recorded yielded a = −0.3335(73) stat (75) syst , in agreement with the SM value a GT = −1/3. A subsequent measurement with more than an order of magnitude higher statistics is still being analyzed [182,323,324]. In the meantime measurements with 19 Ne and 35 Ar have been performed as well [182,321].…”

“…[263][264][265]270] Being commissioned O(0.001) [276] UCNA-Nab-Leuven (LANL) [271,272,276] Analysis ongoing ( 45 Ca) b n < 0.05 [293,294] UCNA (LANL) [390] Ongoing with A n data 0.03 [295] PERKEO III (ILL) [295] Possible with A n data 0.003 [289] Nab (LANL) [188,289,357,358] In preparation 0.001 [291] PERC (Munich) [291,292] Planned a F 0.1% [306] TRINAT (TRIUMF) [306,310] Planned ( 38 K) 0.1% [343] TAMUTRAP (TA&M) [343] Superallowed β p emitters 0.1% [79] WISArD (ISOLDE) [79,177] In preparation ( 32 Ar β p decay) a not stated Ne-MOT (SARAF) [311,312] In preparation ( 18 Ne, 19 Ne, 23 Ne) a GT O(0.1)% [315] 6 He-MOT (Seattle) [313,315] Ongoing ( 6 He) not stated EIBT (Weizmann Inst.) [316][317][318] In preparation ( 6 He) 0.5% [182] LPCTrap (GANIL) [182,321,323,324] Analysis ongoing ( 6 He,…”

First Measurement of Pure Electron Shakeoff in theβDecay of TrappedHe+6Ions

“…The response functions of the β telescope and of the MCPPSD were also included in the MC simulation. It has previously been shown [21] that the shape of the TOF spectrum strongly depends on the ion cloud temperature and on the ions flight distances. The whole simulation was therefore carried out assuming different cloud temperatures around kT = 0.1 eV, and for different positions of the MCPPSD relative to the trap.…”

Precision measurements with LPCTrap at GANIL

“…Simulations have shown that this parameter could also be determined with higher precision, if considered as a free parameter of the fit of the RI ToF distribution [21]. Indeed the shape of the leading edge of this distribution depends strongly on the cloud temperature and not on the value of a  .…”