Two hot issues in neutrino physics

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Rolf Carroll
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1 Bari Xmas Workshop /1/011 Two hot issues in neutrino physics Antonio Palazzo Excellence Cluster Universe - TUM 1

2 Outline! - Introduction - The evidence of! 13 >0 - Hints of new light sterile neutrinos - Conclusions

3 The leptonic mixing Dirac CP-violating phase " is unknown Explicit form: s 3 ~ 0. s 13 ~ 0.0 s 1 ~ 0.31! 3 ~ 3 0! 13 ~ 0! 1 ~ 3 0 3

4 Evidence of non-zero! 13 (June 011) Synopsis of global 3$ oscillation analysis 3 N% !m /10 ev sin " sin " sin " #m -3 /10 ev Fogli, lisi, Marrone, A.P., Rotunno, PRD, (011) [arxiv:110.0] Old reactor fluxes: 3.0 sigma New reactor fluxes: 3. sigma

5 Why a non-zero! 13 is so important J = [U µ3 U e U µu e3] The Jarlskog invariant J gives a parameterization-independent measure of the CP violation induced by the complexity of U In the standard parameterization the expression of J is: J = 1 sin θ 1 sin θ 3 sin θ 13 cos θ 13 sin δ Only if all three! ij = 0 we can have CP violation quark-sector: J CKM ~ 3 x 10-5, much smaller than / J max = lepton-sector: J may be as large as 3 x 10- (it will depend on ") 5

6 Why perturb such a beautiful picture? The 3# scheme explains all data with a few exceptions These seem to point towards sterile neutrino species # s s [singlets of U(1)xSU()] (I) Accumulating hints of ev # s s from oscillation phenomenology and cosmology (II) Indications of warm dark matter from astrophysical small-scale problems (kev # s s are a good option) I will discuss only type-i # s s

7 The 3+1 scheme: How to perturb the standard picture The th # state induces a small perturbation of the 3-flavor framework U s ~ 1!! s $m new >1eV! 3! e! µ"! #" $m atm! 3!! 1 $m sol!! 1 without spoiling its enormous success 7

8 Anomalous # e -disappearance at short-distance Hint #1 Hint # p(measured)/p(predicted) N OBS /(N EXP ) pred,new GALLEX Cr1 1.1 SAGE Cr GALLEX Cr SAGE Ar SAGE coll., PRC 73 (00) 0505 ILL Bugey!3/ ROVNO Krasnoyarsk Goesgen Bugey3 Goesgen Krasnoyarsk!3 Goesgen Krasnoyarsk! Bugey3 PaloVerde CHOOZ In a # framework: P ee 1 sin θ new sin m newl E sin θ new 0.17 ± 0.1 (95%) P ee =1 j>k In a 3+1 scheme: U eju ek sin m jk L E m sol m atm m new Distance to Reactor (m) Mention et al. arxiv:1101:755 [hep-ex] sin θ new U e = sin θ 1 Warning: The culprit may be hidden systematics

9 Fitting the short-distance # e -disappearance "# dof "# contours 1 dof "# profile % % % "# dof "# contour (ev ) "m new !1 1 dof "# profile (ev ) "m new !1 10! !3 10! sin 10! (! new ) 5 10 "# 10! !3 1 FIG.. AllowedMention regionset inal., the PRD sin3 (θ new ) m (011) new plane obtained from the fit of th hypothesis, with sin (θ 13 ) = 0. The left panel is the combination of the reactors an with 51 Cr and 37 Ar radioactive sources. The right panel is the combination of the re data following the method of Ref. [5]. In both cases the ILL energy spectrum info sin θ new 0.1 m new 1 ev Our ILL re-analysis, including only the en- 9

10 Hint #3: Anomalous short-distance # e -appearance Beam Excess Beam Excess p(! _ µ "!_ e,e+ )n p(! _ e,e+ )n other $m (ev /c ) Karmen Bugey CCFR NOMAD % (L max -L <.3) 99% (L max -L <.) L/E! (meters/mev) LSND, PRL 75 m(1995) LSND 050 ev ( matm msol) sin # Giunti and Laveder, arxiv: C. Giunti Phenomenology of Sterile Neutrinos 1 May 011 5/59 Warning: Theory: In tension with disappearance searches: # µ -># e positive appearance signal incompatible with joint # e ># e (positive) & # µ -># µ (negative) searches sin θ eµ 1 sin θ ee sin θ µµ U e U µ Experiments: ~ few %o ~ 0.1 < few % 10

11 Hint #: Cosmology favors extra radiation CMB + LSS tend to prefer extra relativistic content ~ sigma effect [Hamann et al., PRL 105, (010)] Warnings: - It may be a statistical artifact driven by prior effects (Gonzalez-Morales et al., arxiv: ) - ev masses acceptable only abandoning standard %CDM (Kristiansen & Elgaroy arxiv: , Hamann et al. arxiv:110.13) - N eff > at BBN strongly disfavored (Mangano & Serpico PLB 701, 9, 011) - N eff is not specific of # s and can also depend on the epoch (new light particles, decay of dark matter particles, quintessence, ) 11

12 Hint #5: Indication from the solar sector A.P. PRD (011) Warning:! 1 indistinguishable from! 13 1

13 evidence of! 13 >0 eats up hint of! 1 >0 A. P., work in preparation All the rest ALL Upper limit sin θ 1 < 0.05 (90% C.L.) Bound not incompatible with gallium & reactor anomalies 13

14 meaningful to make a combination A. P., work in preparation All the rest All Ga+react In that case non-zero! 1 is rescued and we would have a double indication:! 13 >0 &! 1 >0 at ~ 3& level. 1

15 Summary! - Neutrino data show a robust evidence of non-zero! Way open to CP-violation effects in the lepton sector. - Several anomalies suggest the existence of light # s. - Each indication is problematic and needs further scrutiny. - New experiments are indispensable to settle the issue (VSBL source expts., IceCube, Planck, ) 15

Impact of light sterile!s in LBL experiments "

Xmas Theory Workshop Bari, 22/12/14 Impact of light sterile!s in LBL experiments " Work done in collaboration with L. Klop (Master Thesis at MPI) (now PhD student @ GRAPPA Institute, Amsterdam) Antonio