Elucidating the Electromagnetic Properties of Carlo Giunti INFN, - PowerPoint PPT Presentation

Elucidating the Electromagnetic Properties of Carlo Giunti INFN, Torino, Italy 9-11 November 2019, Chapel Hill, North Carolina, USA Neutrinos with CE ν NS Magnifjcent CE ν NS 2019 2 𝑠 𝜉 ℓℓ′ − Magnifjcent CE ν NS 2019 C. Giunti − Neutrino Electromagnetic Properties − 11 Nov 2019 − 1/18

Neutrino Electromagnetic Interactions a helicity-conserving magnetic electric anapole charge Lorentz-invariant form factors: helicity-fmipping q � H ( ν ) em ( x ) = j ( ν ) ◮ Efgective Hamiltonian: µ ( x ) A µ ( x ) = µ ν j ( x ) A µ ( x ) ν k ( x )Λ kj k , j = 1 ◮ Efgective electromagnetic vertex: ν i ( p i ) ν f ( p f ) Λ � ν f ( p f ) | j ( ν ) µ ( 0 ) | ν i ( p i ) � = u f ( p f )Λ fi µ ( q ) u i ( p i ) q = p i − p f γ ( q ) ◮ Vertex function: � q / q 2 � � � − i σ µν q ν � � Λ µ ( q ) = γ µ − q µ / F Q ( q 2 ) + F A ( q 2 ) q 2 γ 5 F M ( q 2 ) + iF E ( q 2 ) γ 5 q 2 = 0 µ ⇒ ε = − Magnifjcent CE ν NS 2019 C. Giunti − Neutrino Electromagnetic Properties − 11 Nov 2019 − 2/18

Neutrino Charge Radius [Bernabeu et al, PRD 62 (2000) 113012, NPB 680 (2004) 450] 6 2 m 2 dq 2 W G F electromagnetic interactions at the tree-level. vertex ◮ In the Standard Model neutrinos are neutral and there are no ◮ Radiative corrections generate an efgective electromagnetic interaction γ γ � q / q 2 � γ µ − q µ / Λ µ ( q ) = F ( q 2 ) ℓ ℓ W W W ℓ ν ν ν ν � F ( 0 ) + q 2 dF ( q 2 ) + . . . = q 2 � r 2 � � ◮ F ( q 2 ) = ✟✟ ❍❍ ✟ + . . . � ❍ � q 2 = 0 ◮ In the Standard Model: ν e � SM = − 8 . 2 × 10 − 33 cm 2 � r 2 � � m 2 �� ν µ � SM = − 4 . 8 × 10 − 33 cm 2 ℓ � r 2 ν ℓ � SM = − √ 3 − 2 log � r 2 2 π 2 ν τ � SM = − 3 . 0 × 10 − 33 cm 2 � r 2 − Magnifjcent CE ν NS 2019 C. Giunti − Neutrino Electromagnetic Properties − 11 Nov 2019 − 3/18

Experimental Bounds 2009 and the update in Cadeddu, Giunti, Kouzakov, Y.F. Li, Studenikin, Y.Y. Zhang, PRD 98 (2018) 113010, arXiv:1810.05606] [see the review Giunti, Studenikin, RMP 87 (2015) 531, arXiv:1403.6344 1994 90% CHARM-II 1990 90% BNL-E734 2001 90% LSND 1992 Method LAMPF 90% 90% 1992 Krasnoyarsk Experiment Year 90% TEXONO CL Limit [ cm 2 ] ν e �| < 7 . 3 × 10 − 32 |� r 2 ν e e − Reactor ¯ − 4 . 2 × 10 − 32 < � r 2 ν e � < 6 . 6 × 10 − 32 − 7 . 12 × 10 − 32 < � r 2 ν e � < 10 . 88 × 10 − 32 Accelerator ν e e − − 5 . 94 × 10 − 32 < � r 2 ν e � < 8 . 28 × 10 − 32 − 5 . 7 × 10 − 32 < � r 2 ν µ � < 1 . 1 × 10 − 32 Accelerator ν µ e − ν µ �| < 1 . 2 × 10 − 32 |� r 2 − Magnifjcent CE ν NS 2019 C. Giunti − Neutrino Electromagnetic Properties − 11 Nov 2019 − 4/18

1 2 dT because lepton numbers are conserved. F M 3 m 2 4 [Kouzakov, Studenikin, PRD 95 (2017) 055013, arXiv:1703.00401] g p V g n ◮ Neutrino charge radii contributions to ν ℓ – N CE ν NS: � �� � d σ ν ℓ - N ( E ν , T ) = G 2 1 − MT − 1 NF N ( | � q | 2 ) π 2 E 2 ν ���� � � � 2 2 − 2 sin 2 ϑ W − 2 W sin 2 ϑ W � r 2 ν ℓℓ � ZF Z ( | � q | 2 ) + 3 m 2 � �� � V ≃ 0 . 023 � � + 4 W sin 4 ϑ W Z 2 F 2 Z ( | � q | 2 ) |� r 2 ν ℓ ′ ℓ �| 2 9 m 4 ℓ ′ � = ℓ ◮ In the Standard Model there are only diagonal charge radii � r 2 ν ℓ � ≡ � r 2 ν ℓℓ � ◮ Diagonal charge radii generate the coherent shifts � � sin 2 ϑ W → sin 2 ϑ W 1 + 1 W � r 2 ν ℓ � ⇐ ⇒ ν ℓ + N → ν ℓ + N ◮ Transition charge radii generate the incoherent contribution � � W sin 4 ϑ W Z 2 F 2 Z ( | � q | 2 ) |� r 2 ν ℓ ′ ℓ �| 2 ⇐ ⇒ ν ℓ + N → ν ℓ ′ � = ℓ + N 9 m 4 ℓ ′ � = ℓ ℓ ′ � = ℓ − Magnifjcent CE ν NS 2019 C. Giunti − Neutrino Electromagnetic Properties − 11 Nov 2019 − 5/18

COHERENT Neutrino Spectrum and Time stopped pion decays: information allow us to distinguish subsequent muon decays: striking a mercury target. produced by a pulsed proton beam Spallation Neutron Source are 2.0 ◮ Neutrinos at the Oak Ridge Neutrino Spectra ν µ 10 − 13 dN ν / dE [cm − 2 MeV − 1 ] ν µ 1.6 ν e 1.2 0.8 ◮ Prompt monochromatic ν µ from 0.4 π + → µ + + ν µ 0.0 0 5 10 20 30 40 50 ◮ Delayed ¯ ν µ and ν e from the E [MeV] ν µ 2.0 ν µ + ν e µ + → e + + ¯ ν µ + ν e 1.6 ◮ The COHERENT energy and time 1.2 p ν ( t ) 0.8 the interactions of ν e , ν µ , and ¯ ν µ . 0.4 ◮ Note that � r 2 ν ℓℓ ′ � = −� r 2 ν ℓℓ ′ � , but also ¯ 0.0 g p , n ν ) = − g p , n V (¯ V ( ν ) . 0 1 2 3 4 5 6 7 8 9 10 12 t [ µ s] − Magnifjcent CE ν NS 2019 C. Giunti − Neutrino Electromagnetic Properties − 11 Nov 2019 − 6/18

Fits with the old and new quenching factors [Cadeddu, Dordei, Giunti, Y.F. Li, Y.Y. Zhang, arXiv:1908.06045] See also: D. Papoulias, arXiv:1907.11644 A. Khan, W. Rodejohann, arXiv:1907.12444 ◮ Old quenching factor: COHERENT Collaboration, arXiv:1708.01294 ◮ New quenching factor: Collar, Kavner, Lewis, arXiv:1907.04828 − Magnifjcent CE ν NS 2019 C. Giunti − Neutrino Electromagnetic Properties − 11 Nov 2019 − 7/18

Fits with the old and new quenching factors arXiv:1810.05606. quenching factor. CL bounds with the new the statistical reliability. diagonal charge radii are still not competitive with other measurements. the transition charge radii that were not considered [Cadeddu, Dordei, Giunti, Y.F. Li, Y.Y. Zhang, arXiv:1908.06045] 99% CL bounds strengthen before Cadeddu et al, 90% CL (solid) and 99% CL (dashed) 90% CL (solid) and 99% CL (dashed) 100 100 ◮ Free neutron distribution Old quenching Old quenching radii R n ( 133 Cs ) , R n ( 127 I ) . New quenching New quenching 80 80 2 〉 | [10 − 32 cm 2 ] 2 〉 | [10 − 32 cm 2 ] ◮ Slight improvement of 90% 60 60 40 40 | 〈 r ν µτ | 〈 r ν µτ 20 20 ◮ Signifjcant improvement of 0 0 0 20 40 60 80 100 0 20 40 60 80 100 2 〉 | [10 − 32 cm 2 ] 2 〉 | [10 − 32 cm 2 ] | 〈 r ν e µ | 〈 r ν e τ 90% CL (solid) and 99% CL (dashed) 90% CL (solid) and 99% CL (dashed) 100 100 ◮ The bounds on the Old quenching Old quenching New quenching New quenching 80 50 2 〉 | [10 − 32 cm 2 ] 2 〉 [10 − 32 cm 2 ] 60 0 40 ◮ Note the unique bounds on | 〈 r ν e τ 〈 r ν µµ −50 20 −100 0 0 20 40 60 80 100 −100 −50 0 50 100 2 〉 | [10 − 32 cm 2 ] 2 〉 [10 − 32 cm 2 ] | 〈 r ν e µ 〈 r ν ee − Magnifjcent CE ν NS 2019 C. Giunti − Neutrino Electromagnetic Properties − 11 Nov 2019 − 8/18

Fits without transition charge radii [Cadeddu, Dordei, Giunti, Y.F. Li, Y.Y. Zhang, arXiv:1908.06045] cannot fjt the COHERENT data. section is strongly suppressed and 4 Z m 2 3 N neutral current contributions for approximately cancel the weak in the middle: diagonal charge radii. Model, where there are only ◮ Motivated by the Standard 90% CL (solid) and 99% CL (dashed) 100 Old quenching New quenching ◮ Explanation of the excluded area 50 2 〉 [10 − 32 cm 2 ] ◮ The cross section contribution of a diagonal charge radius � r 2 ν ℓ � 0 〈 r ν µ −50 � r 2 ν ℓ � ≃ − W sin 2 ϑ W Free R n −100 ≃ − 26 × 10 − 32 cm 2 −100 −50 0 50 100 2 〉 [10 − 32 cm 2 ] ◮ Around this value the cross 〈 r ν e − Magnifjcent CE ν NS 2019 C. Giunti − Neutrino Electromagnetic Properties − 11 Nov 2019 − 9/18

Neutrino Electric Charges 2 MT 1 V g n g p F M Model. dT ◮ Neutrinos can be millicharged particles in theories beyond the Standard ◮ Neutrino charge contributions to ν ℓ – N CE ν NS: � �� � d σ ν ℓ - N ( E ν , T ) = G 2 1 − MT − 1 NF N ( | � q | 2 ) π 2 E 2 ν ���� � � � 2 W sin 2 ϑ W + 2 − 2 sin 2 ϑ W + 2 m 2 ZF Z ( | � q | 2 ) q ν ℓℓ � �� � V ≃ 0 . 023 � W sin 4 ϑ W � Z ( | � q | 2 ) | q ν ℓℓ ′ | 2 + 4 m 4 Z 2 F 2 M 2 T 2 ℓ ′ � = ℓ ν ℓℓ ′ = − q ν ℓℓ ′ , but also g p , n ν ) = − g p , n ◮ q ¯ V (¯ V ( ν ) . − Magnifjcent CE ν NS 2019 C. Giunti − Neutrino Electromagnetic Properties − 11 Nov 2019 − 10/18

Approximate limits on neutrino millicharges Davidson et al, (1991) [Giunti, Studenikin, RMP 87 (2015) 531, arXiv:1403.6344] [Baumann, Kalus, Gahler, Mampe, PRD 37 (1988) 3107] [Bressi, et al., PRA 83 (2011) 052101, arXiv:1102.2766] A with Neutrality of matter Rafgelt (1999) Red giant cooling (plasmon decay) Limit Solar cooling (plasmon decay) Babu et al, (1993) BEBC beam dump Rafgelt (1999) Reference Gninenko et al, (2006) Neutrality of matter Rafgelt (1999) Method Nuclear reactor Nuclear reactor Studenikin (2013) | q ν e | � 3 × 10 − 21 e | q ν e | � 3 . 7 × 10 − 12 e | q ν e | � 1 . 5 × 10 − 12 e | q ν τ | � 3 × 10 − 4 e SLAC e − beam dump | q ν τ | � 4 × 10 − 4 e | q ν | � 6 × 10 − 14 e | q ν | � 2 × 10 − 14 e ◮ From electric charge conservation in neutron beta decay ( n → p + e − + ¯ ν e ) q mat = Z ( q p + q e ) + Nq n q ν e = q n − ( q p + q e ) = A Z ( q n − q mat ) ◮ q mat = ( − 0 . 1 ± 1 . 1 ) × 10 − 21 e with SF 6 , which has A = 146 . 06 and Z = 70 ◮ q n = ( − 0 . 4 ± 1 . 1 ) × 10 − 21 e ◮ q ν e = ( − 0 . 6 ± 3 . 2 ) × 10 − 21 e − Magnifjcent CE ν NS 2019 C. Giunti − Neutrino Electromagnetic Properties − 11 Nov 2019 − 11/18