Nuclear physics and the new standard model (original) (raw)

Fundamental Symmetries, Neutrons, and Neutrinos (FSNN): Whitepaper for the 2023 NSAC Long Range Plan

Origin of neutrino mass Are there undiscovered forces, weaker than the weak force? Nature of dark matter Baryon asymmetry (violation of B, L, CP) 0νββ Charged LFV (μ→e, e→τ) EDMs, …, n-n oscillations _ Rare / forbidden processes PV electron scattering, Muon g-2, β-decays, … Precision measurements Searches for dark bosons (e-scattering), neutron interferometry … Absolute ν mass, ν scattering, sterile ν,… Light & weakly coupled FIG. 1: The Nuclear Science "targeted program" of research in Fundamental Symmetries, Neutrons, and Neutrinos addresses four interconnected questions about fundamental interactions and the observed universe. looking for the decay. Following the release of the 2015 LRP, a subcommittee report to NSAC [2] listed recommendations related to R&D for some of the key US experimental programs and indicated goals they should accomplish. These goals and others have now been achieved. • Half life limits now exceed 10 26 yr, ten times longer than those existing in 2015. The constraints on m β β now reach near the top of the inverted-ordering mass region and, for some isotopes and nuclear matrix element calculations, even extend a bit into that region. • The CUORE [3], EXO-200 [4], GERDA [5], KamLAND-Zen [6], MAJORANA DEMONSTRATOR [7], and NEXT [8] projects have established experimental programs demonstrating that experiments at the ton scale are feasible. • LEGEND-200 [9] is taking data at LNGS. • CUPID-Mo [10, 11] and CUPID-0 [12] demonstrated energy resolution, radio-purity, and alpha rejection of scintillating bolometers. • SNO+ has measured all of its detector-related backgrounds [13, 14] and shown in bench top studies that it can load up to 3% Te by mass in its scintillator with an acceptable light yield[15]. • SuperNEMO [16] has operated its demonstrator. • Both the nEXO [17] and NEXT [18, 19] collaborations made substantial progress in isolating and detecting a lone Ba ion within a dense Xe environment. The DBD Topical Theory Collaboration [20] led to concerted theoretical effort in 0νβ β decay, involving theorists with expertise in phenomenology, effective field theory (EFT), lattice QCD, and nuclear structure. Much of the US-led progress in ab-initio matrix elements is linked to this Topical Collaboration: • EFT methods for lepton number violation (LNV) beyond the Standard Model [21] and nuclear operators [22, 23], lattice QCD computations of pion-level matrix elements from TeV-scale LNV [24-27], and ab initio 0νβ β nuclear-matrix-element calculations [28-32] all progressed tremendously. • There was great progress in the theory and phenomenology of leptogenesis mechanisms and in the simultaneous analysis of cosmological data, collider data, and 0νβ β decay [33-37]. B. Searches for electric dipole moments A permanent electric dipole moment of a particle or system would imply the presence of a new source of CP violation, which could explain the matter-antimatter asymmetry in the Universe. • The nEDM@SNS experiment, which will use unique cryogenic techniques to make the most precise search for the neutron's EDM, moved from R&D to construction of the apparatus, starting with the cryostats and the magnetic field system. Assembly and testing has now begun at ORNL's SNS [38]. • The LANL nEDM experiment achieved the polarized UCN density required for goal sensitivity [39, 40]. A magnetically shielded room was installed and the magnetic fields characterized. Precession chambers, electrodes, and UCN valves are ready and magnetometers are under development. • Numerous atomic EDM experiments, using methods ranging from vapor cells to optical lattices, improved sensitivity to hadronic CP-violation via nuclear Schiff moments in atoms such as 199 Hg [41], 225 Ra [42, 43], and 129 Xe [44, 45], and a new experiment reported a limit on the 171 Yb EDM [46]. • Work with radioactive pear-shaped nuclei, which are extremely sensitive to hadronic CP violation, has made major progress [47]: the Ra EDM work mentioned above, the first spectroscopy on a radioactive molecule, RaF [48], and the first control of radium-containing molecular ions [49, 50]. • Limits on the electron EDM were improved by an order of magnitude by the ACME [51] and JILA [52, 53] experiments, which leverage internal molecular electric fields. The YbF [54] and NL-EDM eEDM [55] experiments made major improvements in laser-cooling [56] and trapping [57]. • Atomic electron-EDM experiments with Cs [58] and Fr [59] continued their push to leverage quantum science methods. Several new molecular approaches are under development, including lasercooled polyatomics [60, 61] and matrix-isolated diatomics [62]. • Molecular eEDM methods are being expanded to search for hadronic CP violation, both through nuclear Schiff moments and magnetic quadrupole moments, in several active experiments, including CeNTREX [63], YbOH [60, 64], and YbF [65] and several others in initial stages of development. • The phenomenology of EDMs was connected with physics at the energy frontier [66-69]. The ways in which the EDM program and LHC complement each other in exploring the origin of CP violation and the Universe's matter-antimatter asymmetry are now much better understood [70-72]. • Lattice QCD calculations of the nucleon EDM have appeared [73-81], paving the way for results with quantified uncertainties. At the nuclear level, we have new Schiff moment computations [82-84]. Progress in ab initio techniques promises ab initio calculations of Schiff moments soon [85]. C. Parity-violating electron scattering Parity violation in electron-nucleon scattering is a powerful tool for both for uncovering BSM physics and for examining nuclei. • Qweak at Jefferson Lab (JLab) carried out a high-precision elastic electron-proton scattering parityviolating (PV) asymmetry measurement [86], providing the most precise low-energy determination of the weak mixing angle and setting constraints on new semi-leptonic multi-TeV scale PV physics. • Also at JLab, elastic electron-nucleus PV asymmetry measurements (PREX (Pb-208) [87] and CREX (Ca-48) [88]) provided the most accurate constraints on neutron skins, challenging models of neutron-rich matter and facilitating the next-generation experiments MOLLER and SoLID. D. Precision beta decay with nuclei Nuclear beta decay provides precision tests of the Standard Model and probes BSM physics. • The 0 + → 0 + superallowed-beta-decay data set was refined. Updated theoretical corrections revealed some tension in CKM unitarity and tightened constraints on exotic scalar currents [89]. • There was progress in tests of CKM unitarity in mirror nuclei, in half-lives (37 K [90] and 21 Na [91] at TAMUTRAP, 25 Al [92], 11 C [93], 13 N [94], 15 O [95], and 29 P [96] at Notre Dame); Q EC-values (11 C [97], 21 Na, and 29 P [98] at NSCL); and β-asymmetries (37 K [99] with TRINAT). • Cyclotron Radiation Emission Spectroscopy (CRES), which promises dramatic improvements in sensitivity to exotic couplings through precision spectroscopy, was demonstrated in 6 He and 19 Ne [100]. • High-precision angular-correlation measurements to improve limits on exotic scalar and tensor currents were performed in 8 Li [101, 102] and 8 B at the BPT at Argonne's ATLAS facility [103], in 6 He at Washington [104], and in 37 K at TRINAT [99]. • A new dispersion-theoretical calculation of the inner radiative corrections in neutron and nuclear beta decay reduced the associated theoretical uncertainty [105]. New nuclear-structure-dependent effects were discovered [106]. E. Precision beta decay with neutrons The neutron is the simplest nucleus that undergoes beta decay and provides a particularly clean laboratory for BSM searches. • The UCNτ collaboration performed the most precise measurement of the free neutron lifetime at LANL [107] and set new limits on neutron dark decay [108], leveraging improvements at what is now one of the world's brightest UCN sources [39]. • The UCNA collaboration published its final results for the neutron β-asymmetry, measured with UCN, thereby resolving tension among previous measurements [109]. It also extracted first and improved limits on the BSM Fierz term [110, 111] and set new limits on dark neutron decay [112]. • The aCORN experiment at NIST completed two runs and published a new measurement of the electron-antineutrino angular correlation (a coefficient) in free neutron β-decay with final uncertainty 1.7% [113, 114].

Neutrinos and the Standard Model

Neutrino Physics - Its Impact on Particle Physics, Astrophysics and Cosmology - Proceedings of the Carolina Symposium on Neutrino Physics, 2001

Since their "discovery" by Pauli in 1930, neutrinos have played a key part in confirmation of the structure of the standard model of strong and electroweak interactions. After reviewing ways in which this has been manifested in the past, we discuss areas in which neutrinos continue to play this role.

The Standard Model of Particle Physics: Status and Low-Energy Tests

ESO ASTROPHYSICS SYMPOSIA, 2003

Precision measurements of low-energy observables provide stringent tests of the Standard Model structure and accurate determinations of its parameters. An overview of the present experimental status is presented. The main topics discussed are the muon anomalous magnetic moment, the asymptotic freedom of strong interactions, the lepton universality of gauge couplings, the quark flavour structure and CP violation.

Probing nucleon strangeness with neutrinos: Nuclear model dependences

Physical Review C, 1996

The extraction of the nucleon's strangeness axial charge, ∆s, from inclusive, quasielastic neutral current neutrino cross sections is studied within the framework of the plane-wave impulse approximation. We find that the value of ∆s can depend significantly on the choice of nuclear model used in analyzing the quasielastic cross section. This model-dependence may be reduced by one order of magnitude when ∆s is extracted from the ratio of total proton to neutron yields. We apply this analysis to the interpretation of low-energy neutrino cross sections and arrive at a nuclear theory uncertainty of ±0.03 on the value of ∆s expected to be determined from the ratio of proton and neutron yields measured by the LSND collaboration. This error compares favorably with estimates of the SU(3)-breaking uncertainty in the value of ∆s extracted from inclusive, polarized deep-inelastic structure function measurements. We also point out several general features of the quasielastic neutral current neutrino cross section and compare them with the analogous features in inclusive, quasielastic electron scattering.

Through Neutrino Eyes: The Search for New Physics

Advances in High Energy Physics, 2015

The year 2014 will mark the 60th anniversary since the neutrino detector of Frederick Reines and Clyde L. Cowan, Jr. was turned (neutrino detection in 1956). After many years, Super-Kamiokande showed in 1998 that neutrinos are massive. Today, neutrino physics has become a very active research field: there is a plethora of different neutrino experiments and theoretical studies. Subsequent measurements [2-6] of the two neutrino mass squared differences and the leptonic mixing parameters lead to a phase of precision experiments in neutrino physics. Recently the last remaining mixing angle, the 1-3 mixing angle, has been measured by the Daya Bay , Double Chooz [9, 10], and RENO [11] experiments after initial hints by T2K [12] and MINOS . Contrary to theoretical expectations from flavor symmetry considerations, it turned out to be large.

Low energy probes of physics beyond the standard model

Progress in Particle and Nuclear Physics, 2013

Low-energy tests of fundamental symmetries and studies of neutrino properties provide a powerful window on physics beyond the Standard Model (BSM). In this article, we provide a basic theoretical framework for a subsequent set of articles that review the progress and opportunities in various aspects of the low-energy program. We illustrate the physics reach of different low-energy probes in terms of an effective BSM mass scale and illustrate how this reach matches and, in some cases, even exceeds that accessible at the high energy frontier.

The Long-Baseline Neutrino Experiment: Exploring Fundamental Symmetries of the Universe

2013

The preponderance of matter over antimatter in the early Universe, the dynamics of the supernova bursts that produced the heavy elements necessary for life and whether protons eventually decay --- these mysteries at the forefront of particle physics and astrophysics are key to understanding the early evolution of our Universe, its current state and its eventual fate. The Long-Baseline Neutrino Experiment (LBNE) represents an extensively developed plan for a world-class experiment dedicated to addressing these questions. LBNE is conceived around three central components: (1) a new, high-intensity neutrino source generated from a megawatt-class proton accelerator at Fermi National Accelerator Laboratory, (2) a near neutrino detector just downstream of the source, and (3) a massive liquid argon time-projection chamber deployed as a far detector deep underground at the Sanford Underground Research Facility. This facility, located at the site of the former Homestake Mine in Lead, South D...