New bounds on neutrino magnetic moments Particle Physics

New bounds on neutrino magnetic moments “Particle Physics and Cosmology” XXIII Rencontres de Blois 31/05/2011 Alexander Moscow Studenikin State University & JINR Dubna

Outline Neutrino magnetic moments (critical) comments on recently obtained and published experimental bounds on … the claim that experimental bounds on can be significantly improved if atomic ionization mode in ν-e scattering is accounted for …

K. Kouzakov, A. Studenikin, “Magnetic neutrino scattering on atomic electrons revisited” Phys. Lett. B 105 (2011) 061801, ar. Xiv: 1011. 5847 “Electromagnetic neutrino-atom collisions: The role of electro to appear in Nucl. Phys. B (Proc. Supp. ) 2011 (Proc. of Neutrino Oscillation Workshop 2010) K. Kouzakov, A. Studenikin, M. Voloshin, “Neutrino-impact ionization of atoms in search for neutrino magnetic moment”, ar. Xiv: 1101. 4878, 25 Jan 2011 Phys. Rev. D (2011) , accepted for publication “On neutrino-atom scattering in searches for neutrino magne moments” ar. Xiv: 1102. 0643, 3 Feb 2011 Nucl. Phys. B (Proc. Supp. ) 2011 (Proc. of Neutrino 2010 Conference) “Testing neutrino magnetic moment in ionization of atoms by neutrino impact”, ar. Xiv: 1105. 5543, 27 May 2011 JETP Lett. 93 (2011) 699 M. Voloshin, “Neutrino scattering on atomic electrons in search for neutrino magnetic moment” Phys. Rev. Lett. 105 (2010) 201801, ar. Xiv: 1008. 2171

Outline (II) A short review on neutrino electromagnetic properties ( including magnetic moments ) Conclusions

Carlo Giunti, Alexander Studenikin : “Neutrino electromagnetic properties” Phys. Atom. Nucl. 73, 2089 -2125 (2009) ar. Xiv: 0812. 3646 v 5, Apr 12, 2010 A. Studenikin : “Neutrino magnetic moment: a window to new physics” Nucl. Phys. B (Proc. Supl. ) 188, 220 (2009) C. Giunti, A. Studenikin : “Electromagnetic properties of neutrin J. Phys. : Conf. Series. 203 (2010) 012100 ar. Xiv: 1006. 3646 June 8, 2010 C. Giunti, A. Studenikin : “Theory and phenomen of neutrino electromagnetic properties” Rev. Mod. Phys. (in preparation)

Why magnetic moment of ?

…Why electromagnetic properties of provide a kind of window / bridge to NEW Physics ?

… in spite of results of terrestrial laboratory experi on EM properties as well as data from astrophysics and cosmology are in agreement with “ZERO” EM … However, in course of recent development o knowledge on mixing and oscillat

… a tool for studying physics beyond the Stand

… much greater values are desired for astrophysical or cosmology visualization of

…the present status… to have visible is not an easy task for theoreticians and experimentalists

… puzzling electromagnetic properties something that is tiny or probably even does not exist at all…

exhibits unexpected properties (p “ Pauli himself wrote to “ E. Fermi, 1933 …recent claim for new experimental bound on (with atomic ionization Baade: effect) continue chain of puzzles… “Today I did something a physicist should I predicted something which will never be experimentally. . . ".

q electromagnetic vertex function Matrix element of electromagnetic current is a Lorentz vector p´ p should be constructed using matrices tensors vectors and Lorentz covariance (1) and electromagnetic gauge invariance (2)

Matrix element of electromagnetic current between neutrino states where vertex function generally contains 4 form factors , 1. electric dipole 2. magnetic 3. electric Hermiticity and discrete symmetries of EM current factors Dirac EM properties put constraints on form Majorana 1) CP invariance + hermiticity =0, 2) at zero momentum transfer only electric charge and magnetic moment contribute to , 3) hermiticity itself are real: 4. anapole three form factors. = 0 1) from CPT invariance (regardless CP or CP ). …as early as 1939, W. Pauli… a way to distinguish Dirac and Majorana

In general case matrix element of different initial and final can be considered between states of different masses … beyond SM… and form factors are matrices in mass eigenstates space. ( off-diagonal case Dirac 1) hermiticity itself does not apply restrictions on form factors, ) Majorana 1) CP invariance + hermiticity or 2) CP invariance + hermiticity o , … quite different EM properties … are relatively real (no relative phases).

… importance of If studies diagonal were confirmed Dirac then Majorana … for non-diagonal = transitional … progress in experimental studies of

magnetic moment in experiments Samuel Ting ( wrote on the wall at Department of Theoretical Physics of Moscow State University ) : “Physics is an experimental science”

Studies of ν-e scattering - most sensitive method of experimental investigation of Cross-section: where the Standard Model contribution T is the electron recoil energy a for anti-neutrin to incorporate charge radius:

Magnetic moment contribution is dominated at lo recoil energies when and … the lower the smallest measurable electron recoil ene the smaller values of can be probed in scattering from A. Starostin

MUNU experiment at Bugey reactor (2005) TEXONO collaboration at Kuo-Sheng power plant (2006) GEMMA (2007) GEMMA I 2005 - 2007 BOREXINO (2008) …was considered as the world best const Montanino, Picariello, Pulido, PRD 2008 based on first release of BOREXINO data

GEMMA (2005 -2008) Germanium Experiment on measurement of Magnetic Moment of Antineutrino NR (Dubna) + ITEP (Moscow) at Kalinin Nuclear Power P …till 13 January 2010 and again since autumn 20 best limit on magnetic moment A. Beda et al, Phys. Atom. Nucl. Lett. 7 (2010) 406 result known since 2009: A. Beda, E. Demidova, A. Starostin et al, ar. Xiv: 09. 06. 1926 , June 10, 2009, A. Beda, V. Brudanin, E. Demidova et al, in: “Particle Physics on the Eve of LHC”, ed. A. Studenikin, World Scientific (Singapore), p. 112, 2009 (13 th Lomonosov Conference) www. icas. ru

… quite recent claim H. Wong et al. (TEXONO that ν-e cross section Coll. ), ar. Xiv: 1001. 2074, should be increased by 13 Jan 2010, reported at Atomic Ionization effect: Neutrino 2010 ? Conference (Athens, June 2010), PRL 105 (2010) 061801 …new bounds …

…much better limits on effective magnetic m H. Wong et al. , (TEXONO Coll. ar. Xiv: 1001. 2074 13 Jan 2010, PRL 105 … atomic ionization effect accounted for … (2010) 061801 ? Neutrino 2010 Conference, Athens … however … ? A. Beda et al. (GEMMA Coll. ), … atomic ionization effect accounted for … ar. Xiv: 1005. 2736, 16 May 2010 … ν-e scattering on free electrons … (without atomic ionization)

K. Kouzakov, A. Studenikin, “Magnetic neutrino scattering on atomic electrons revisited” Phys. Lett. B 105 (2011) 061801, ar. Xiv: 1011. 5847 “Electromagnetic neutrino-atom collisions: The role of electro to appear in Nucl. Phys. B (Proc. Supp. ) 2011 (Proc. of Neutrino Oscillation Workshop 2010) K. Kouzakov, A. Studenikin, M. Voloshin, “Neutrino-impact ionization of atoms in search for neutrino magnetic moment”, ar. Xiv: 1101. 4878, 25 Jan 2011 Phys. Rev. D (2011) , accepted for publication “On neutrino-atom scattering in searches for neutrino magne moments” ar. Xiv: 1102. 0643, 3 Feb 2011, Nucl. Phys. B (Proc. Supp. ) 2011 (Proc. of Neutrino 2010 Conference) “Testing neutrino magnetic moment in ionization of atoms by neutrino impact”, ar. Xiv: 1105. 5543, 27 May 2011 JETP Lett. 93 (2011) 699 M. Voloshin, “Neutrino scattering on atomic electrons in search for neutrino magnetic moment” Phys. Rev. Lett. 105 (2010) 201801, ar. Xiv: 1008. 2171

No important effect of Atomic Ionization on cross section in experiments once all possible final electronic states accounted for M. Voloshin, 23 Aug 2010; K. Kouzakov, A. Studenikin, 26 Nov 2010; H. Wong et al, ar. Xiv: 1001. 2074 V 3, 28 Nov 2010

Neutrino-impact ionization of atoms in in serarch for → q scattering on atoms (Ge) at low energy t → p T ~ few ke. V and lower so that → p' Ge atom recoil energy , interaction with nucleus is neglect scattering on atomic e is importa Four momentum transfer Kouzakov, q = p – p' Studenikin, 2010; Kouzakov, Studenikin, energy and spatial momentum Voloshin, 2011 transfer from neutrinos to atomic electrons

Double differential ν-e cross section Kouzakov, Studenikin, 2010 Kouzakov, Studenikin, Voloshin, 2011 where dynamical structure factor (Van Hove, 1954) Fourier transforms of electron density and cur and summ is over all states of electron system,

For single-differential inclusive cross section measured i transversal contribution practically for most is negligible SM electroweak contribution to cross section nonrelativistic limit For free electron , f electro approximatio … the same for electron bound in atom … is v (ν-e scattering on free electrons)

GEMMA (2005 -2008) Germanium Experiment on measurement of Magnetic Moment of Antineutrino NR (Dubna) + ITEP (Moscow) at Kalinin Nuclear Power P …till 13 January 2010 and again since autumn 2 best limit on magnetic moment A. Beda et al, Phys. Atom. Nucl. Lett. 7 (2010) 406 result known since 2009: A. Beda, E. Demidova, A. Starostin et al, ar. Xiv: 09. 06. 1926 , June 10, 2009, A. Beda, V. Brudanin, E. Demidova et al, in: “Particle Physics on the Eve of LHC”, ed. A. Studenikin, World Scientific (Singapore), p. 112, 2009 (13 th Lomonosov Conference) www. icas. ru

Conclusions

e. m. vertex function charge dipole 4 form factors magnetic and electric anapole EM properties distinguish Dirac and Majorana In extensions of SM ( a way to ): enhancement of, even electrically millicharged magnetic moment Limits from reactor ν-e Limits from astrophysic scattering experiments (2009, 2010): star cooling (1990): A. Beda et al. (GEMMA Coll. ) G. Raffelt

is “presently known” to be in the range 11 provides a tool for exploration possible physics beyond the Standard Model Due to smallness of neutrino-mass-induced magnetic moments, any indication for non-trivial electromagnetic properties of , that could be obtained within reasonable time in the future, would give evidence for interactions beyond extended Standard Model