Scattering of neutrinos on a polarized electron target as a test for new physics beyond the standard model

Abstract

In this paper, we analyze the scattering of the neutrino beam on the polarized electron target, and predict the effects of two theoretically possible scenarios beyond the Standard Model. In both scenarios, Dirac neutrinos are assumed to be massive.First, we consider how the existence of CP violation phase between the complex vector V and axial A couplings of the Left-handed neutrinos affects the azimuthal dependence of the differential cross section. This asymmetry does not vanish in the massless neutrino limit. The azimuthal angle φ e ′ of outgoing electron momentum is measured with respect to the transverse component of the initial electron polarization η ⊥ e . We indicate the possibility of using the polarized electron target to measure the CP violation in the νµe − scattering. The future superbeam and neutrino factory experiments will provide the unique opportunity for the leptonic CP violation studies, if the large magnetized sampling calorimeters with good event reconstruction capabilities are build.Next, we take into account a scenario with the participation of the exotic scalar S coupling of the Right-handed neutrinos in addition to the standard vector V and axial A couplings of the Lefthanded neutrinos. The main goal is to show how the presence of the R-handed neutrinos, in the above process changes the spectrum of recoil electrons in relation to the expected Standard Model prediction, using the current limits on the non-standard couplings. The interference terms between the standard and exotic couplings in the differential cross section depend on the angle α between the transverse incoming neutrino polarization and the transverse electron polarization of the target, and do not vanish in the limit of massless neutrino. The detection of the dependence on this angle in the energy spectrum of recoil electrons would be a signature of the presence of the R-handed neutrinos in the neutrino-electron scattering. To make this test feasible, the polarized artificial neutrino source needs to be identified.

An active electron polarized scintillating GSO target for neutrino physics

“…A new generation of neutrino experiments could stem using detectors based on this mechanism, as suggested in several theoretical papers [4][5][6]. It has been pointed out that investigation of the flavor composition of a (anti)neutrino beam could be possible by studying their scattering from polarized electrons in a polarized target [7].…”

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

“…It is worth reminding that the PET has been proposed to test the flavor composition of (anti)neutrino beam [20] and various effects of non-standard physics. We mean the neutrino magnetic moments, TRSV in the leptonic processes [21], axions, spin-spin interaction in gravitation [22][23][24][25][26][27][28] The possibility of using polarized targets of nucleons and of electrons for the fermionic, scalar and vector dark matter detection is also worth noticing [29][30][31]. The methods of producing the spin-polarized gasses such as helium, argon and xenon are described in [32,33].…”

Scattering processes could distinguish Majorana from Dirac neutrinos

“…In order to do that, we will consider that neutrinos are unpolarized and that the electron in the target is polarized. The possible use of polarized electrons in ν-e elastic scattering has been previously proposed in order to look for other non-standard neutrino interactions, as the neutrino magnetic moment itself [18], or possible C P violation signals [19] among other different motivations [20]. An efficient Polarized Electron Target (PET) can be obtained applying strong, although realistic, magnetic fields to the detector [18,19].…”

“…The possible use of polarized electrons in ν-e elastic scattering has been previously proposed in order to look for other non-standard neutrino interactions, as the neutrino magnetic moment itself [18], or possible C P violation signals [19] among other different motivations [20]. An efficient Polarized Electron Target (PET) can be obtained applying strong, although realistic, magnetic fields to the detector [18,19]. Putting aside for the moment the technical difficulties in order to have such PET detector, here we will show that the electron polarization could enhance the difference between Dirac and Majorana neutrinos as long as neutrinos had lost their initial polarization due to an interaction of the neutrino with external magnetic fields in some wild astrophysical environment.…”