Right-handed Dirac neutrinos in ν e– scattering and azimuthal asymmetry in recoil electron event rates

2018

Self Cite

In this paper, we indicate a possibility of utilizing the elastic scattering of the Dirac low energy (∼ 1 MeV) electron neutrinos (ν e 's) on the polarized electron target (PET) in testing the time reversal symmetry violation (TRSV). We consider a scenario in which the incoming ν e beam is the superposition of left chiral (LC) and right chiral (RC) states. LC ν e 's interact mainly by the standard V − A and small admixture of non-standard scalar S L , pseudoscalar P L , tensor T L interactions, while RC ones are only detected by the exotic V + A and S R , P R , T R interactions. In addition, one assumes that the spin polarization vector of the initial ν e 's is turned aside from its momentum, and due to this the nonvanishing transversal component of the ν e spin polarization appears. We compute the differential cross section as a function of the recoil electron azimuthal angle and scattered electron energy, and show how the interference terms between standard V − A and exotic S R , P R , T R couplings depend on the various angular correlations among the transversal ν e spin polarization, the polarization of the electron target, the incoming neutrino momentum and the outgoing electron momentum in the limit of relativistic ν e . We illustrate how the maximal value of recoil electrons azimuthal asymmetry and the asymmetry axis location of outgoing electrons depend on the azimuthal angle of the transversal component of the ν e spin polarization, both for the time reversal symmetry conservation (TRSC) and TRSV. Next, we display that the electron energy spectrum and polar angle distribution of the recoil electrons are also sensitive to the interference terms between V − A and S R , P R , T R couplings, proportional to the T-even and T-odd angular correlations among the transversal ν e polarization, the electron polarization of the target, and the incoming ν e momentum, respectively. Our modelindependent analysis is carried out for the flavor ν e 's. To a make such tests feasible, the intense (polarized) artificial ν e source, PET and the appropriate detector measuring the directionality of the outgoing electrons, and/or the recoil electrons energy with a high resolution have to be identified.

Section: Elastic Scattering Of Dirac Electron Neutrinos On Polarized mentioning

confidence: 99%

On possibility of time reversal symmetry violation in neutrino elastic scattering on polarized electron target

2018

Self Cite

“…[108], where the muon capture by proton as the production process of leftright chiral superposition has been considered. The formula for the longitudinal component of the ν polarisation contains the terms from the LCh ν's produced in the V − A interaction and RCh ones generated in the exotic (S, T, P) R interactions.…”

Section: Elastic Scattering Of Dirac Electron Neutrinos Off Unpolarismentioning

confidence: 99%

“…This in general would modify the dependence of the event number on the exotic couplings and would introduce new ones (cf. [108]) enlarging the number of degrees of freedom. This issue requires thorough follow-up studies.…”

Section: Elastic Scattering Of Dirac Electron Neutrinos Off Unpolarismentioning

confidence: 99%

Probing neutrino nature at Borexino detector with chromium neutrino source

2016

Self Cite

In this paper, we indicate a possibility of utilizing the intense chromium source (∼370 PBq) in probing the neutrino nature in low energy neutrino experiments with the ultra-low threshold and background real-time Borexino detector located near the source (∼8 m). We analyse the elastic scattering of electron neutrinos (Dirac or Majorana, respectively) on the unpolarised electrons in the relativistic neutrino limit. We assume that the incoming neutrino beam is the superposition of left-right chiral states produced by the chromium source. Left chiral neutrinos may be detected by the standard V − A and non-standard scalar S L , pseudoscalar P L , tensor T L interactions, while right chiral ones partake only in the exotic V + A and S R , P R , T R interactions. Our model-independent study is carried out for the flavour (current) neutrino eigenstates. We compute the expected event number for the standard V − A interaction of the left chiral neutrinos using the current experimental values of standard couplings and in the case of left-right chiral superposition. We show that the significant decrement in the event number due to the interference terms between the standard and exotic interactions for the Majorana neutrinos may appear. We also demonstrate how the presence of the exotic couplings affects the energy spectrum of outgoing electrons, both for the Dirac and Majorana cases. The 90 % C.L. sensitivity contours in the planes of corresponding exotic couplings are found. The presence of interferences in the Majorana case gives the stronger constraints than for the Dirac neutrinos, even if the neutrino source is placed outside the detector.

“…As an example of process in which the transversal ν polarization may be produced, we refer to the ref. [86], where the muon capture by proton has been considered. The amplitude for the ν e e − scattering in low energy region is of the form:…”

Section: Elastic Scattering Of Dirac Electron Neutrinos On Polarized mentioning

confidence: 99%

Neutrino elastic scattering on polarized electrons as a tool for probing the neutrino nature

2020

Self Cite

Possibility of using the polarized electron target (PET) for testing the neutrino nature is considered. One assumes that the incoming electron neutrino (ν e ) beam is the superposition of left chiral states with right chiral ones. Consequently the non-vanishing transversal components of ν e spin polarization may appear, both T-even and T-odd. ν e s are produced by the low energy monochromatic (un)polarized emitter located at a near distance from the hypothetical detector which is able to measure both the azimuthal angle and polar angle of the recoil electrons, and/or also the energy of the outgoing electrons with a high resolution. A detection process is the elastic scattering of ν e s (Dirac or Majorana) on the polarized electrons. Left chiral (LC) ν e s interact mainly by the standard V − A interaction, while right chiral (RC) ones participate only in the non-standard V + A, scalar S R , pseudoscalar P R and tensor T R interactions. We show that a distinction between the Dirac and Majorana ν e s is possible both for the purely left chiral states and the left-right superposition. In the first case a departure from the standard prediction of the azimuthal asymmetry of recoil electrons is caused by the interferences between the non-standard complex S and T couplings, proportional to the angular correlations (T-even and T-odd) among the polarization of the electron target, the incoming neutrino momentum and the outgoing electron momentum. Such a deviation would indicate the Dirac nature of ν e s. In the second variant the azimuthal asymmetry, polar distribution and energy spectrum of scattered electrons are sensitive to the interference terms between the standard and exotic interactions, proportional to the various angular correlations (T-even and T-odd) among the transversal ν e spin polarization (related to the ν e source), the electron target polarization, the incoming ν e momentum and the outgoing electron momentum. The basic difference a between the Dirac and Majorana ν e s arises from the absence of T and V interactions in the Majorana scenario. Moreover, in the Majorana case the above observables contain the non-vanishing interference between V − A and V + A interactions, proportional to the T-even longitudinal ν e polarization. Our model-independent study is carried out for the flavor ν e eigenstates in the relativistic ν e limit.