Measurement of the induced pseudoscalar form factor in the capture of polarized muons by Si nuclei

Induced pseudoscalar coupling of the proton weak interaction

“…By 'recommended values for g p /g a ' we mean our assessment of the best values from the current world experimental dataset and the most complete model calculations. In quoting these values we combined the experimental results of Possoz et al (1974), Possoz et al (1977), Roesch et al (1981b) and Kuno et al (1984) to obtain a world average of the helicity amplitude ratio X = 0.23 ± 0.06 for 12 C(0 + , 0)→ 12 B(1 + , 0) and combined the experimental results of Brudanin et al (1995), Moftah et al (1997) and Briançon et al (2000) to obtain a world average of the helicity amplitude ratio X = 0.55 ± 0.04 for 2201). 23 For the hyperfine dependence on 11 B we employ the results of Wiaux et al (2002) and for the hyperfine dependence on 23 Na we employ the results of Johnson et al (1996).…”

“…Also recently a new measurement of all the coefficients has been performed at the Dubna phasotron by Brudanin et al (1995) and Briançon et al (2000). To identify both (α + 2 3 c 1 ) and b 2 the authors recorded the Doppler spectra for different values of P µ ·k.…”

“…To identify both (α + 2 3 c 1 ) and b 2 the authors recorded the Doppler spectra for different values of P µ ·k. In Brudanin et al (1995) they used forward/backward positioned Ge detectors to vary P µ ·k and in Briançon et al (2000) they used µ spin precession to vary P µ ·k. In analyzing their data the authors enforced the dynamical relations between correlation coefficients and fit the 2201 keV lifetime and 2170 keV mixing ratio.…”

Muon capture on35Cl

“…However their interpretations are complicated by muon chemistry in 1 H and 2-body currents in 3 He, and the puzzling discrepancy between the values of g p from RMC on 1 H and OMC on 3 He is so far unexplained. In complex nuclei new results from allowed transitions on 11 B [10], 23 Na [11] and 28 Si [12][13][14] are also available. In nuclei the difficulty is disentangling the weak dynamics from nuclear structure.…”

Recoil alignment in muon capture onN14

“…Moreover, in complex nuclei its medium modification -due to effects that range from core polarization and exchange currents to partial restoration of chiral symmetry [5][6][7] -are of considerable interest. Unfortunately, the world data on g p from exclusive capture on complex nuclei is rather sparse, it comprising the study of recoil orientations in allowed Gamow-Teller transitions on 12 C [8][9][10][11] and 28 Si [12][13][14], the study of hyperfine effects in allowed Gamow-Teller transitions on 11 B [15,16] and 23 Na [17,18], and the measurement of the 16 O(0 + , 0) → 16 N(0 − , 120) first-forbidden transition rate [19][20][21]. While the majority of these experiments are in agreement with the chiral prediction for the induced coupling, the result of g p /g a = 1.0 [4] from the 28 Si experiments is in stark disagreement with the theoretical expectation.…”