beta decays
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Particles ◽  
2021 ◽  
Vol 4 (4) ◽  
pp. 521-535
Author(s):  
Steven Ragnar Stroberg

We review the status of ab initio calculations of allowed beta decays (both Fermi and Gamow–Teller), within the framework of the valence-space in-medium similarity renormalization group approach.


2021 ◽  
Vol 2021 (10) ◽  
Author(s):  
B. Belfatto ◽  
Z. Berezhiani

Abstract Recent high precision determinations of Vus and Vud indicate towards anomalies in the first row of the CKM matrix. Namely, determination of Vud from beta decays and of Vus from kaon decays imply a violation of first row unitarity at about 3σ level. Moreover, there is tension between determinations of Vus obtained from leptonic Kμ2 and semileptonic Kℓ3 kaon decays. These discrepancies can be explained if there exist extra vector-like quarks at the TeV scale, which have large enough mixings with the lighter quarks. In particular, extra vector-like weak singlets quarks can be thought as a solution to the CKM unitarity problem and an extra vector-like weak doublet can in principle resolve all tensions. The implications of this kind of mixings are examined against the flavour changing phenomena and SM precision tests. We consider separately the effects of an extra down-type isosinglet, up-type isosinglet and an isodoublet containing extra quarks of both up and down type, and determine available parameter spaces for each case. We find that the experimental constraints on flavor changing phenomena become more stringent with larger masses, so that the extra species should have masses no more than few TeV. Moreover, only one type of extra multiplet cannot entirely explain all the discrepancies, and some their combination is required, e.g. two species of isodoublet, or one isodoublet and one (up or down type) isosinglet. We show that these scenarios are testable with future experiments. Namely, if extra vector-like quarks are responsible for CKM anomalies, then at least one of them should be found at scale of few TeV, and anomalous weak isospin violating Z-boson couplings with light quarks should be detected if the experimental precision on Z hadronic decay rate is improved by a factor of 2 or so.


Particles ◽  
2021 ◽  
Vol 4 (4) ◽  
pp. 397-468
Author(s):  
Chien-Yeah Seng

We review some recent progress in the theory of electroweak radiative corrections in semileptonic decay processes. The resurrection of the so-called Sirlin’s representation based on current algebra relations permits a clear separation between the perturbatively-calculable and incalculable pieces in the O(GFα) radiative corrections. The latter are expressed as compact hadronic matrix elements that allow systematic non-perturbative analysis such as dispersion relation and lattice QCD. This brings substantial improvements to the precision of the electroweak radiative corrections in semileptonic decays of pion, kaon, free neutron and JP=0+ nuclei that are important theory inputs in precision tests of the Standard Model. Unresolved issues and future prospects are discussed.


2021 ◽  
Vol 81 (9) ◽  
Author(s):  
P. Adhikari ◽  
R. Ajaj ◽  
M. Alpízar-Venegas ◽  
P.-A. Amaudruz ◽  
D. J. Auty ◽  
...  

AbstractThe DEAP-3600 detector searches for the scintillation signal from dark matter particles scattering on a 3.3 tonne liquid argon target. The largest background comes from $$^{39}\text{ Ar }$$ 39 Ar beta decays and is suppressed using pulse-shape discrimination (PSD). We use two types of PSD estimator: the prompt-fraction, which considers the fraction of the scintillation signal in a narrow and a wide time window around the event peak, and the log-likelihood-ratio, which compares the observed photon arrival times to a signal and a background model. We furthermore use two algorithms to determine the number of photons detected at a given time: (1) simply dividing the charge of each PMT pulse by the mean single-photoelectron charge, and (2) a likelihood analysis that considers the probability to detect a certain number of photons at a given time, based on a model for the scintillation pulse shape and for afterpulsing in the light detectors. The prompt-fraction performs approximately as well as the log-likelihood-ratio PSD algorithm if the photon detection times are not biased by detector effects. We explain this result using a model for the information carried by scintillation photons as a function of the time when they are detected.


Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1388
Author(s):  
Mannque Rho

I discuss how the axial current coupling constant gA renormalized in scale symmetric chiral EFT defined at a chiral matching scale impacts on the axial current matrix elements on beta decays in nuclei with and without neutrinos. The “quenched” gA observed in nuclear superallowed Gamow–Teller transitions, a long-standing puzzle in nuclear physics, is shown to encode the emergence of chiral-scale symmetry hidden in QCD in the vacuum. This enables one to explore how trace-anomaly-induced scale symmetry breaking enters in the renormalized gA in nuclei applicable to certain non-unique forbidden processes involved in neutrinoless double beta decays. A parallel is made between the roles of chiral-scale symmetry in quenching gA in highly dense medium and in hadron–quark continuity in the EoS of dense matter in massive compact stars. A systematic chiral-scale EFT, presently lacking in nuclear theory and potentially crucial for the future progress, is suggested as a challenge in the field.


2021 ◽  
Vol 62 (3) ◽  
Author(s):  
Hiroyasu Ejiri
Keyword(s):  

Author(s):  
Izyan Hazwani Hashim ◽  
Hiroyasu Ejiri

This is a brief review on ordinary muon capture (OMC) experiments at Research Center for Nuclear Physics (RCNP) Osaka University relevant for the study of double beta decays (DBDs) and astro anti-neutrinos (neutrino) nuclear responses. OMC usually leaves the nucleus in highly excited unbound state. OMC is a charge exchange reaction via the charged weak boson as given by (μ,vμ) reactions with μ and vμ being the muon and muon neutrino. Subjects discussed include 1) unique features of OMC for studying DBDs and astro anti-neutrino (neutrino) nuclear responses, 2) experiments of OMCs on 100Mo and natMo to study neutrino nuclear responses for DBDs and astro anti-neutrinos, 3) impact of the OMC results on neutrino nuclear responses for DBDs and astro anti-neutrinos. Remarks and perspectives on OMC experiments for neutrino nuclear responses are briefly described.


Author(s):  
Misheck Kirimi

Our knowledge of electricity is based on two nearly parallel concepts – charge and electron. The charge concept is symmetrical: nature has equal numbers of positive and negative charges playing equivalent roles in atoms. The electron concept has two asymmetries. One, the observable universe has more positive than negative electrons. Two, atoms contain negative- but no positive electrons. Here I propose that charge is static electron and electron is moving charge. That is, resting (electrostatic) and moving (electrodynamic) behaviours exclusively make charge and electron different. The proposal reveals previously unnoticed symmetries in the electron concept and has experimental backing. Faraday, Stoney and Millikan observed charges in static conditions – electrolytes, oil drops, doorknobs etc. In contrast, Thomson and Anderson observed electrons at high speeds in cathode tubes and cloud chambers. Beta decays were initially interpreted to mean existence of electrons in atomic nuclei[i]. Equating ‘charge’ to ‘static electron’ reinstates and validates the interpretation. Brown, L. M. Nuclear structure and beta decay (1932–1933), American Journal of Physics 56, 982 (1988).


2021 ◽  
Vol 9 ◽  
Author(s):  
Hiroyasu Ejiri

Fundamental properties of neutrinos are investigated by studying double beta decays (ββ-decays), while atro-neutrino nucleo-syntheses and astro-neutrino productions are investigated by studying inverse beta decays (inverse β-decays) induced by astro-neutrinos. Neutrino nuclear responses for these ββ and β-decays are crucial for these neutrino studies in nuclei. This reports briefly perspectives on experimental studies of neutrino nuclear responses (square of nuclear matrix element) for ββ-decays and astro-neutrinos by using nuclear and leptonic (muon) charge-exchange reactions


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