Decoherence in supernova neutrino transformations suppressed by deleptonization

Abstract

In the dense-neutrino region at 50 -400 km above the neutrino sphere in a supernova, neutrino-neutrino interactions cause large flavor transformations. We study when the multiangle nature of the neutrino trajectories leads to flavor decoherence between different angular modes. We consider a two-flavor mixing scenario between e and another flavor x and assume the usual hierarchy F e > F e > F x F x for the number fluxes. We define F e ÿ F e =F e ÿ F x as a measure for the deleptonization flux which is the one crucial parameter. The transition between the quasi-single-angle behavior and multiangle decoherence is abrupt as a function of . For typical choices of other parameters, multiangle decoherence is suppressed for * 0:3, but a much smaller asymmetry suffices if the neutrino mass hierarchy is normal and the mixing angle small. The critical depends logarithmically on the neutrino luminosity. In a realistic supernova scenario, the deleptonization flux is probably enough to suppress multiangle decoherence.

Mu-tau neutrino refraction and collective three-flavor transformations in supernovae

“…[21,22], only two-flavor conversions driven by m 2 atm and the small 13 have thus far been studied. We here extend our previous numerical solutions [17] to the case of three neutrino flavors. Our main results can be summarized as follows: (i) A two-flavor treatment indeed captures the full effect if one ignores V and if the ordinary Mikheyev-Smirnov-Wolfenstein (MSW) resonances occur outside of the collective neutrino region.…”

“…We solve them numerically as previously described [17], now using 3 3 matrices instead of polarization vectors. The factor 1 ÿ v q v p in the Hamiltonian implies ''multiangle effects'' for neutrinos moving on different trajectories [8,9,11].…”

“…where the Hamiltonian is [23] In spherical symmetry the EOMs can be expressed as a closed set of differential equations along the radial direction [17,20]. We solve them numerically as previously described [17], now using 3 3 matrices instead of polarization vectors.…”

“…In a recent series of papers [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] it was recognized, however, that the traditional picture was not complete: neutrino-neutrino interactions cause large collective flavor transformations in the SN region out to a few 100 km (gray shaded region in Fig. 1).…”

Symmetries in collective neutrino oscillations

“…In fact, some studies seem to suggest that collective neutrino oscillations in the isotropic and anisotropic environments can be very different. For example, collective neutrino oscillations of the bipolar type can experience "kinematic decoherence" and be disrupted in anisotropic environments [26,27]. Additionally, a very large matter background can result in neutrino oscillation phase differences between different neutrino trajectories in an anisotropic neutrino gas [10], and this effect recently has been shown to result in suppression of collective neutrino oscillations [28].…”