On the flavor composition of the high-energy neutrinos in IceCube

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• 作者：Sergio Palomares-Ruiz^a ; ^{Sergio.Palomares.Ruiz@ific.uv.es" class="auth_mail" title="E-mail the corresponding author} ; Olga Mena^a ; ^{omena@ific.uv.es" class="auth_mail" title="E-mail the corresponding author} ; Aaron C. Vincent^a ; ^b ; ^{aaron.vincent@durham.ac.uk" class="auth_mail" title="E-mail the corresponding author}
• 关键词：high-energy neutrinos ; IceCube ; flavor ratios
• 刊名：Nuclear and Particle Physics Proceedings
• 出版年：2016
• 出版时间：April-June 2016
• 年：2016
• 卷：273-275
• 期：Complete
• 页码：433-439
• 全文大小：467 K

文摘

The IceCube experiment has recently released 3 years of data of the first ever detected high-energy (class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S2405601415005520&_mathId=si1.gif&_user=111111111&_pii=S2405601415005520&_rdoc=1&_issn=24056014&md5=ce9d4a9a0934e56dabaeece7a098e8dc" title="Click to view the MathML source">≳30TeVclass="mathContainer hidden">class="mathCode">$\gtrsim 30\text{TeV}$) neutrinos, which are consistent with an extraterrestrial origin. In this talk, we compute the compatibility of the observed track-to-shower ratio with possible combinations of neutrino flavors with relative proportion class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S2405601415005520&_mathId=si2.gif&_user=111111111&_pii=S2405601415005520&_rdoc=1&_issn=24056014&md5=98e2146c40ef6175ab159c13e9ce77b1" title="Click to view the MathML source">(α_e:α_μ:α_τ)_⊕class="mathContainer hidden">class="mathCode">${({\alpha }_e:{\alpha }_{\mu }:{\alpha }_{\tau })}_{\oplus }$. Although this observation is naively favored for the canonical (1 : 1 : 1)_⊕ at Earth, once we consider the IceCube expectations for the atmospheric muon and neutrino backgrounds, this flavor combination presents some tension with data. We find that, for an astrophysical neutrino class="mathmlsrc">title="View the MathML source" class="mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S2405601415005520&_mathId=si3.gif&_user=111111111&_pii=S2405601415005520&_rdoc=1&_issn=24056014&md5=8497146ea809c9d21381520c7da21dee">class="imgLazyJSB inlineImage" height="20" width="30" alt="View the MathML source" title="View the MathML source" src="/sd/grey_pxl.gif" data-inlimgeid="1-s2.0-S2405601415005520-si3.gif">class="mathContainer hidden">class="mathCode">$E_{\nu }^{-2}$ energy spectrum, (1 : 1 : 1)_⊕ at Earth is currently disfavored at 92% C.L. We discuss the trend of this result by comparing the results with the 2-year and 3-year data. We obtain the best-fit for (1 : 0 : 0)_⊕ at Earth, which cannot be achieved from any flavor ratio at sources with averaged oscillations during propagation. Although it is not statistically significant at present, if confirmed, this result would suggest either a misunderstanding of the expected background events, or a misidentification of tracks as showers, or even more compellingly, some exotic physics which deviates from the standard scenario.