Parity Violation In Atomic Physics Research Articles

U boson interpolating between a generalized dark photon or dark Z , an axial boson, and an axionlike particle

A light boson $U$ from an extra $U(1)$ interpolates between a generalized dark photon coupled to $Q,\ B$ and $L_i$ (or $B-L$), plus possibly dark matter, a dark $Z$ coupled to the $Z$ current, and one axially coupled to quarks and leptons. We identify the corresponding $U(1)_F$ symmetries, with $F= \gamma_Y Y+\gamma_B B+\gamma_{L_i}L_i+\gamma_A F_A+\gamma_{F'}F'\!+\gamma_d F_d$, $F_d$ acting in a dark sector and $F'$ on possible semi-inert BEH doublets uncoupled to quarks and leptons. The $U$ current is obtained from the $U(1)_F $ and $Z$ currents, with a mixing determined by the spin-0 BEH fields. The charge $Q_U$ of chiral quarks and leptons is a combination of $Q,\ B,\ L_i$ and $T_{3L}$ with the axial $F_A$. It involves in general isovector and isoscalar axial terms, in the presence of two BEH doublets. A longitudinal $U$ with axial couplings has enhanced interactions, and behaves much as an axionlike particle. Its axial couplings $g_A$, usually restricted to $< 2\times 10^{-7} m_U$(MeV), lead to effective pseudoscalar ones $g_P= g_A\times 2m_{q,l}\,/m_U=2^{1/4}\, G_F^{1/2}\, m_{q,l} \ A_\pm $. $\,A_\pm$ is proportional to an invisibility parameter $r=\cos\theta_A$ induced by a singlet v.e.v., possibly large and allowing the $U$ to be very weakly interacting. This allows for a very small gauge coupling, expressed with two doublets and a singlet as $g"\!/4\simeq 2\times 10^{-6} m_U$(MeV) $ r/\sin 2\beta$. We discuss phenomenological implications for meson decays, neutrino interactions, atomic-physics parity violation, naturally suppressed $\pi^0\to\gamma U$ decays, etc.. The $U$ boson fits within the grand-unification framework, in symbiosis with a $SU(4)_{\rm es }$ electrostrong symmetry broken at the GUT scale, with $Q_U$ depending on $Q,\ B-L,\ F_A$ and $T_{3A}$ through three parameters $\gamma_Y,\ \gamma_A$ and $\eta$.

Metastable states, the adiabatic theorem and parity violating geometric phases II

We discuss and calculate parity conserving (PC) and parity violating (PV) geometric phases for the metastable 2S states of hydrogen and deuterium. The atoms are supposed to be subjected to slowly varying electric and magnetic fields which act as external parameters for the atoms. Geometric flux density fields are introduced which allow for an easy overview how to choose the paths in parameter space in order to obtain only PC or only PV geometric phases. The PV phases are calculated in the Standard Model of particle physics. Even if numerically they come out small they have interest of principle as a new manifestation of parity violation in atomic physics.

Global study of electron-quark contact interactions

We perform a global fit of data relevant to eeqq contact interactions, including deep inelastic scattering at high Q{sup 2} from ZEUS and H1, atomic physics parity violation in cesium from JILA, polarized e{sup {minus}} on nuclei scattering experiments at SLAC, Mainz and Bates, Drell-Yan production at the Fermilab Tevatron, the total hadronic cross section {sigma}{sub had} at CERN LEP, and neutrino-nucleon scattering from CCFR. With only the new DESY HERA data, the presence of contact interactions improves the fit compared to the standard model. When other data sets are included, the size of the contact contributions is reduced and the overall fit represents no real improvement over the standard model. {copyright} {ital 1997} {ital The American Physical Society}

ELECTRO-WEAK NEUTRAL CURRENTS

Experimental information on weak neutral currents is reviewed. New data are mostly from weak-electromagnetic interference, over a very large q range : from P violation in atomic transitions to ee~ annihilation at q of more than 1000 GeV. Excellent agreement is observed with the minimal GlashowSalam-Weinberg theory, even though some basic assumptions are not so well tested, as yet. INTRODUCTION Since the experimental discovery' of weak neutral currents in 1973, most results and phenomenology on this subject' have come from neutrino experiments,essentially deep inelastic neutrino scattering (vN •*• vX) and elastic neutrino-electron scattering (ve -»• ve). A decisive step occurred in 1978 with the discovery of parity violation in neutral currents as manifested through their interference with the known electromagnetic current : this was observed at very low q in atomic spectroscopy' and in inelastic electron-deuteron scattering at moderate q **' . All these data lead with minimal assumptions to a unique solution for the electron, u and d-quark couplings which were found to be consistent' with the standard Glashow-Salam-Weinberg theory'. At this conference, for the first time, the emphasis of new data is clearly on weak-electromagnetic interference -the occurrence of weak neutral effects in processes described, some years ago, only in terms of quantum electrodynamics. These results provide measurements of new couplings, giving us insight into the weak interactions of the 2i and 33 generations of fermions. Extended q range — from atomic physics to high energy ee annihilation —proves to be. essential to rule out some non-standard theories. This talk will cover the following subjects with their implications : I. Notations ; standard GSW model. II. Neutrino results : the I*generation (e,u,d) couplings. III. e e annihilation into lepton pairs : e,y,x couplings and lepton universality. n d IV. Deep inelastic muon scattering : sin8 from the 2 generation. V. Parity violation in atomic physics : low q test of the theory. VI. e e annihilation into hadrons : heavy quark couplings. VII. Tests of the standard theory. VIII. Discussion on alternatives to the standard theory. Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1982372

The value of sin 2θw in atomic physics experiments

The one-loop electroweak radiative corrections to parity violation in atomic physics are calculated in the context of the standard SU(2) × U(1) model. We find that the corrections are small and that the effective value of sin 2 θ w in such experiments is 0.219 ± 0.014 to be compared with 0.227 ± 0.010 deduced from high energy neutrino-nucleon scattering.

Alternative searches for parity violation in atomic physics

The effects of parity-violating weak neutral currents on two-photon and autoionization transitions in atoms are considered.

Hierarchy of symmetry breakings and neutral currents in anSU(6) grand unification model

In anSU(6) grand unification model with eight quarks and eight leptons belonging to 15-plet and singlet representations, the symmetry is spontaneously broken by the sequenceSU(6)→SU(3) c ×SU(2)×U(1)×U(1)→SU(3) c ×U(1). Fror two cases of symmetry breakings the effective weak neutral current coupling constants are compared with experiment. For theSU(3) c ×SU(2)×U(1)×U(1)×→SU(3) c ×U(1) symmetry breaking, the coupling constants reproduce the Weinberg-Salam model with a small correction term. Agreement with the experimental mean values is improved with the correction term. Parity violation in atomic physics is also discussed.

Gauge-theory predictions for deep-inelastic polarized-electron-nucleon scattering asymmetries

Asymmetries between the deep-inelastic scattering of right- and left-handed electrons by nucleons predicted by three distinct models of weak and electromagnetic interactions are compared. We find that even a left-right--symmetric model, for which neutral currents conserve parity in lowest order, predicts sizeable asymmetries as a result of radiative corrections. Asymmetry measurements are contrasted with atomic-physics parity-violation searches and the relevance of our results for an ongoing experiment is discussed.

Ambidextrous theory of the weak interactions

We construct a renormalizable model of weak interactions based on the gauge group SU(2) L × SU(2) R × U(1) and incorporating a natural suppression of all flavor-changing neutral currents. We resolve the dilemma between the observations of the “high- y anormaly” and of parity-violating neutral currents in neutrino physics. Parity violation in atomic physics is predicted to be smaller than in the standard gauge model. The decay μ → ey need not be absolutely forbidden. The theory requires two charged and two neutral intermediate vector bosons with masses between 50 and 200 GeV; and at least six quark flavors, three charged leptons, and three massive neutral leptons.

The smallest SU(2) × U(1) gauge model and parity violation in atomic physics

Under a general class of assumptions we show that the present data for partiy violating effects in atomic bismuth and for inclusive neutral current neutrino (anti-) nucleon scattering exclude all SU(2) × U(1) gauge models except one, as far as the light quarks and light leptons are concerned. Furthermore the smallness of parity violation in Bi is a strong evidence for the existence of right-handed charged weak current.

What is the weak charge of the electron?

The experimental results on $$\bar \nu _\mu $$ -electron scattering, when interpreted withinSU 2×U 1 theories, put severe constraints on the weak charge of the right-handed electron. Under very general assumptions it is shown that the casesI 3 weak (e R − )=0 or − 1/2 are possible. The caseI 3 weak (e R − )=+1/2 is found to be unlikely. All other assignments for e R − are excluded. Consequences for parity violation in atomic physics are discussed.

Neutral currents: The probe of gauge theories

A comprehensive evaluation of SU(2) × U(1) gauge model predictions for elastic and inclusive neutral current reactions is made. The standard 4-quark model yields acceptable agreement with all neutrino neutral current data. However a minimal 5-quark model indicated by ν N charged current data provides a better description of νp → νp elastic scattering. Inclusive neutral current predictions of the 4- and 5- quark models are identical for the experimentally favored value of the Weinberg angle, sin 2θ W = 3 8 . Experiments on parity violation in atomic physics can readily distinguish the gauge model possibilities. We give predictions for neutral current diffractive production of vector and axial vector mesons. We make quantitative estimates of the interesting phenomena to be expected if there exists a charm changing neutral current. These include (i) an energy dependence of the inclusive neutral current cross section, (ii) fake lepton non-conservation at the 10 −2 level in ν N and the 10 −3 level in νN, (iii) complete D 1 0 − D 2 0 mixing giving like-sign dileptons and ΔS = 2 events in neutrino scattering, and (iv) neutral current decays of D 1,2 0 giving neutrino trilepton events. Lastly, we examine neutral current contributions in the test of the universality of free fall.

The U3(W)-gauge theory III: Atomic physics parity-violation

It is shown how a slight natural generalization of the mechanism of the spontaneous gauge symmetry breaking in the U3(W) gauge theory (Pandit 1976) can accommodate the degree of parity-violation in atomic physics suggested by some recent experiments, along with the neutral current processes involving the neutrinos.

Constraints in quark and lepton models

We investigate quark and lepton models in SU(2) ⊗ U(1) theory derived from two theoretical assumptions — natural absence of strangeness and μe flavor changing neutral currents and absence of Adler-Bell-Jackiw anomalies — and currently known weak interaction phenomenologies including the negative search for the parity violation in atomic physics. The simplest model has seven quarks (four Q = 2 3 quarks and three Q = − 1 3 quarks). Other possible models with exotic quarks (i.e. with Q = − 4 3 , 5 3 ) are also discussed.

A New Vectorlike Model of the Weak Interactions

A vectorlike model of the weak interactions with six quark flavors is proposed. The model is based on the gauge theory with the group SU (2) XU (1). It is shown that the model well describes the rise of the ratio of li- to v-induced total cross sections by the charged current. Discussions on the various weak phenomena including the parity violation in atomic physics are given. Gauge theory is interesting as a candidate for the so-called unified theory m particle physics. 1l In the framework of the gauge theory, many kinds of models can be considered. Hovvever, any meaningful model must be free from the triangle anomalies which destroy the renormalizability.'l The anomalies are most naturally removed in the vector like model. 1l Furthermore, the vectorlike model has very interesting properties. For example, we might be able to understand, in the frame­ work of the vectorlike gauge theory, that the left-right asymmetry of nature 1s caused by the spontaneous symmetry breaking. Recently several authors have proposed the models of this kind. 3l One of the characteristic features of their models is that the hadronic neutral current is purely vector type. Therefore their models predict, for instance, O'Nc/ ONc = 1, where Oxc(O'Nc) stands for the inclusive neutrino (antineutrino) cross section by the neu­ tral current. However, experimental data show an apparent departure from their predictions. The most recent data indicate if~c/ O~c<0.61 ± 0.25, where D denotes the averaged nucleon target.') The vectorlike models with the parity violating neutral current have been already proposed.sl,Bl In the model of the Kanazawa group, quark flavors transform as triplets under the weak SU (2), and an artificial angle relation has been assumed in order to guarantee the universality of the charged current. sl The Barnett's model 1 6) is very beautiful and well describes the anomaly in ifcc at high energies with bottom-quark mass ~5 Ge V, where ifcc is the antineutrino-nucleon inclusive cross section by the charged current.7l,lll His model predicts opposite sign for the parity violation in atomic physics compared with the prediction of the conventional GIM modeP0l for Bi atom, if the transformation properties of the lepton sector are reasonably chosen.8l

Weak neutral currents in the U3(W)-gauge theory of weak and electromagnetic interactions

A discussion is given of the implications of the recently proposed U3(W)-gauge theory of weak and electromagnetic interactions (Pandit 1976) for some phenomena resulting from its weak neutral currents: (1) neutrino-electron scattering, (2) neutrino-nucleon elastic and inelastic scattering, (3) coherent neutrino-nucleus scattering (4) weak interaction effects ine + e −→μ+μ− and (5) parity-violation in atomic physics. The theory agrees quite well with the available experimental results on neutrino processes. We find the coherent neutrino-nucleus cross-section for Fe56 to be about 6 times larger than that in the WS-GIM theory giving some hope of accounting for supernova explosion by the resulting neutrino-radiation pressure.