Unparticle physics and neutrino phenomenology

We have constrained unparticle interactions with neutrinos and electrons using available data on neutrino-electron elastic scattering and the four CERN LEP experiments data on mono photon production. We have found that, for neutrino-electron elastic scattering, the MUNU experiment gives better constraints than previous reported limits in the region $d>1.5$. The results are compared with the current astrophysical limits, pointing out the cases where these limits may or may not apply. We also discuss the sensitivity of future experiments to unparticle physics. In particular, we show that the measurement of coherent reactor neutrino scattering off nuclei could provide a good sensitivity to the couplings of unparticle interaction with neutrinos and quarks. We also discuss the case of future neutrino-electron experiments as well as the International Linear Collider.

Figure 1

Limits on the parameters $d$ and ${\lambda }_{0,1}=\sqrt{{\lambda }_{0,1\nu }^{e\beta }{\lambda }_{0,1e}}$ (90% C.L.) from the MUNU experiment for the scalar unparticle case (black solid line) and for the vector unparticle cases, both for flavor changing currents (gray solid line) and for the flavor conserving case (dashed line). Previous bounds obtained by Balantekin and Ozansoy (BO) [14] (dots and triangles) are shown for comparison. The present analysis based on the MUNU data gives stronger constraints on ${\lambda }_{0,1}$ for values of $d>1.5$.

Figure 2

Differential cross section for $\nu -e$ scattering for the SM case and for the vector unparticle case. We show both the flavor conserving as well as the flavor changing case. In the flavor conserving interaction mediated by unparticles, the negative interference term gives a different spectral shape. The effective coupling ${\lambda }_1=\sqrt{{\lambda }_{1\nu }^{\alpha \beta }{\lambda }_{1e}}$ was fixed to ${\lambda }_1=5.5\times {10}^{-5}$ and $d=1.2$.

Figure 3

Limits on the parameters $d$ and ${\lambda }_{1e}$ for the unparticle analysis of the four CERN LEP experiments at 90% C.L. considering $\Lambda =1\mathrm{TeV}$.

Figure 4

Future sensitivity of the TEXONO proposal (90% C.L.) on the unparticle dimension $d$ and the effective coupling $\lambda$. Scalar case corresponds to $\lambda =\sqrt{{\lambda }_{0\nu }^{e\beta }{\lambda }_{0d}}$ (black solid line). Vector flavor conserving for $\lambda =\sqrt{{\lambda }_{1\nu }^{ee}{\lambda }_{1d}}$ (dashed line) and vector flavor changing $\lambda =\sqrt{{\lambda }_{1\nu }^{e\beta }{\lambda }_{1d}},\beta =\mu$, $\tau$ (gray solid line). Limits were done assuming ${\lambda }_{0,1u}=0$. The flavor conserving case, which includes the interference term, is the most sensitive.

Figure 5

Current constraints on vectorial unparticle couplings ${\lambda }_1$ and $d$ from reactor neutrino $\nu -e$ elastic scattering (MUNU experiment). The current astrophysical limits are shown for comparison, although both for the SN1987A and the Eötvös case a different initial hypothesis should be considered (see text for details.)