海量文库 文档专家
当前位置:首页 >> >>

Verifiable Origin of Neutrino Mass at TeV Scale

UCRHEP-T317 September 2001

Veri?able Origin of Neutrino Mass at TeV Scale

arXiv:hep-ph/0109270v1 27 Sep 2001

Ernest Ma Department of Physics, University of California, Riverside, CA 92521, USA

Abstract The physics responsible for neutrino mass may reside at or below the TeV energy scale. The neutrino mass matrix in the (νe , ν? , ντ ) basis may then be deduced from future high-energy accelerator experiments. The newly observed excess in the muon anomalous magnetic moment may also be related.

————– Talk given at the 7th International Workshop on Topics in Astroparticle and Underground Physics, Assergi, Italy (September 8-12, 2001)



The conventional wisdom in neutrino physics is that the origin of neutrino mass is at a very high energy scale, say 1013 GeV or greater, in which case there is no hope of veri?cation experimentally. On the other hand, recent papers [1, 2, 3] have shown that it is just as natural to have the origin of neutrino mass at the TeV scale and be amenable to direct experimental veri?cation. In the minimal Standard Model with one Higgs doublet Φ = (φ+ , φ0 ) and 3 lepton doublets L = (ν, l)L and singlets lR only, neutrino mass must come from the e?ective dimension-5 operator [4, 5] 1 1 LLΦΦ = (νφ0 ? lφ+ )2 , Λ Λ (1)

which shows that the form of mν must necessarily be “seesaw”, i.e. v 2 /Λ where v = φ0 , whatever the underlying mechanism for neutrino mass is. The canonical seesaw mechanism [6] assumes 3 heavy right-handed singlet lepton ?elds NR with the Yukawa couplings f LNΦ and the Majorana mass mN , hence Eq.(1) is realized with the famous expression mν = f 2v2 . mN (2)

Note that lepton number is violated by mN in the denominator and it should be large for a small neutrino mass, i.e. mν ? f 1.0

1013 GeV mN





Higgs Triplet Model

An equally satisfactory realization of Eq.(1) is to use a Higgs triplet [7, 8] ξ = (ξ ++ , ξ + , ξ 0) with √ Lint = fij [ξ 0 νi νj + ξ + (νi lj + li νj )/ 2 + ξ ++ li lj ] √ ? + ?(ξ 0 φ0 φ0 ? 2ξ ? φ+ φ0 + ξ ?? φ+ φ+ ) + H.c.


This model violates lepton number explicitly, but if the parameter ? is set to zero, it becomes the Gelmini-Roncadelli model [9], which is now experimentally ruled out. On the other hand, with ? = 0 and m2 positive and large, i.e. mξ >> v, we have instead [8] ξ mν = 2fij ?v 2 = 2fij ξ 0 . 2 mξ (5)

Note that the e?ective operator of Eq.(1) is realized here with a simple rearrangement of the individual terms, i.e. Li Lj ΦΦ = νi νj φ0 φ0 ? (νi lj + li νj )φ+ φ0 + li lj φ+ φ+ . (6)

Note also that lepton number is violated in the numerator in this case. If fij ? 1, then ?/m2 < 10?13 GeV?1 . Hence mξ ? 1 TeV is possible, if ? < 100 eV. To obtain such a small ξ mass parameter, the “shining” mechanism of extra large dimensions [10] may be used. In
+ + that case, the doubly charged ξ ±± can be easily produced at colliders and ξ ++ → li lj is

a distinct and backgroundless decay which maps out |fij |, and thus determine directly the neutrino mass matrix of Eq. (5) up to an overall scale.[1] This model also predicts observable ? ? e conversion in nuclei within the sensitivity of proposed future experiments.


Leptonic Higgs Doublet Model

Another simple and interesting way to have the origin of neutrino mass at the TeV scale has recently been proposed.[2] As in the canonical seesaw model, we have again 3 NR ’s but they 3

are now assigned L = 0 instead of the customary L = 1. Hence the Majorana mass terms are allowed but the usual LNΦ terms are forbidden by lepton-number conservation. The LLΦΦ operator of Eq.(1) is not possible and mν = 0 at this point. We now add a new scalar doublet η = (η + , η 0 ) with L = ?1, then f LNη is allowed, and the operator LLηη will generate a nonzero neutrino mass if η 0 = 0. The trick now is to show how f η 0 < 1 MeV can be obtained naturally, so that mN ? 1 TeV becomes possible and amenable to experimental veri?cation, in contrast to the very heavy NR ’s of the canonical seesaw mechanism. Consider the following Higgs potential: V 1 1 = m2 Φ? Φ + m2 η ? η + λ1 (Φ? Φ)2 + λ2 (η ? η)2 1 2 2 2 + λ3 (Φ? Φ)(η ? η) + λ4 (Φ? η)(η ?Φ) + ?2 (Φ? η + η ? Φ), 12 (7)

where the ?2 term breaks lepton number softly and is the only possible such term. Let 12 φ0 = v, η 0 = u, then the equations of constraint for the minimum of V are given by v[m2 + λ1 v 2 + (λ3 + λ4 )u2 ] + ?2 u = 0, 1 12 u[m2 + λ2 u2 + (λ3 + λ4 )v 2 ] + ?2 v = 0. 2 12 Consider the case m2 < 0, m2 > 0, and |?2 | << m2 , then 1 2 12 2 v2 ? ? m2 1 , λ1 u?? ?2 v 12 . m2 + (λ3 + λ4 )v 2 2 (10) (8) (9)

Hence u may be very small compared to v(= 174 GeV). For example, if m2 ? 1 TeV, |?2 | ? 10 GeV2 , then u ? 1 MeV and 12 mν ? f 1.0

1 TeV mN



Since both mN and m2 are now of order 1 TeV, they may be produced at future colliders and be detected. (I) If m2 > mN , then the physical charged Higgs boson h+ , which is mostly 4

η + , will decay into N, which then decays into a charged lepton and a W boson via ν ? N miixing:
+ h+ → li Nj , ± Nj → lk W ? .


(II) If mN > m2 , then
± Ni → lj h? ,

h+ → t? b,


the latter coming from Φ ? η mixing. In either case, m2 and mN can be determined kinematically, and |fij | measured up to an overall scale. In summary, the particle spectrum of the leptonic Higgs doublet model consists of the usual Standard-Model particles, including the one physical Higgs boson h0 , 3 heavy NR ’s 1 at the TeV scale, and a heavy scalar doublet (h± , h0 , A) of individual masses ? m2 . The 2 charged Higgs boson h± can be pair-produced at hadron colliders, whereas NR (h± ) can be produced at lepton colliders via the exchange of h± (NR ).


The Size of Lepton Number Violation

It has been shown in the above that whereas Majorana neutrino masses have to be tiny, the actual magnitude of lepton number violation may come in all sizes. (1) Large: mN ? 1013 GeV in the canonical seesaw mechanism. (2) Medium: |?2 | ? 10 GeV2 in the leptonic Higgs doublet model with mN ? 1 TeV. 12 (3) Small: ? ? 10 eV in the Higgs triplet model (mξ ? 1 TeV) with a singlet bulk scalar in extra large dimensions. In (2) and (3), direct experimental determination of the relative magnitudes of the elements of Mν is possible at future colliders.



Muon Anomalous Magnetic Moment

The recent measurement [11] of the muon anomalous magnetic moment appears to disagree with the Standard-Model prediction [12] by 2.6σ, i.e. ?a? = aexp ? aSM > 215 × 10?11 ? ? (14)

at 90% con?dence level. The origin of this discrepancy may be directly related to the TeV physics responsible for neutrino mass. If the leptonic Higgs doublet model [2] is combined with a similar model of quark masses [13] to become a supersymmetric model [14] with 4 ? ? Higgs doublets, then the loop contribution of N and h+ will in general cause the transition li → lj γ. Hence there are predictions [3] for the muon anomalous magnetic moment as well as lepton ?avor violating processes such as ? → eγ, τ → ?γ, etc. If the neutrino mass matrix is hierarchical, then Eq. (14) implies B(τ → ?γ) > 8.0×10?6 , which contradicts the experimental upper bound of 1.1 × 10?6 . To avoid this restriction, the neutrino mass matrix has to be nearly degenerate, in which case we have the interesting prediction of Γ(τ → eγ) Γ(τ → ?γ) Γ(? → eγ) : : 5 5 m? mτ m5 τ 1 1 = (?m2 )2 : (?m2 )2 : (?m2 )2 , sol sol atm 2 2 where bimaximal mixing has been assumed. In Fig. (1), the branching fractions of τ → ?γ and ? → eγ, and the ? ? e conversion ratio in


Al are plotted using the lower bound of Eq. (14), as a function of the common neutrino

mass mν . The values (?m2 )atm = 3 × 10?3 eV2 , (?m2 )sol = 3 × 10?5 eV2 , (16)

have been chosen according to present data from neutrino-oscillation experiments. At mν ? 0.2 eV, which is in the range of present upper limits on mν from neutrinoless double beta 6

decay, B(? → eγ) and R?e are both at their present experimental upper limits. Hence Eq. (15) will be tested in new experiments planned for the near future which will lower these upper limits.



Physics at the TeV scale may reveal the true origin of neutrino mass, so that accelerator experiments will become complementary to nonaccelerator experiments in determining the neutrino mass matrix without ambiguity.



This work was supported in part by the U. S. Department of Energy under Grant No. DEFG03-94ER40837.



This talk was being given in Assergi, Italy on September 11, 2001, at the moment the infernal attack on the World Trade Center in New York began. All of humanity is the victim today and for years to come.

[1] E. Ma, M. Raidal, and U. Sarkar, Phys. Rev. Lett. 85, 3769 (2000); hep-ph/0012101 (Nucl. Phys. B, in press). [2] E. Ma, Phys. Rev. Lett. 86, 2502 (2001).


[3] E. Ma and M. Raidal, Phys. Rev. Lett. 87, 011802 (2001); Z.-Z. Xing, Phys. Rev. D64, 017304 (2001). [4] S. Weinberg, Phys. Rev. Lett. 43, 1566 (1979). [5] E. Ma, Phys. Rev. Lett. 81, 1171 (1998). [6] M. Gell-Mann, P. Ramond, and R. Slansky, in Supergravity, edited by P. van Nieuwenhuizen and D. Z. Freedman (North-Holland, Amsterdam, 1979), p. 315; T. Yanagida, in Proceedings of the Workshop on the Uni?ed Theory and the Baryon Number in the Universe, edited by O. Sawada and A. Sugamoto (KEK, Tsukuba, Japan, 1979), p. 95; R. N. Mohapatra and G. Senjanovic, Phys. Rev. Lett. 44, 912 (1980). [7] J. Schechter and J. W. F. Valle, Phys. Rev. D22, 2227 (1980). [8] E. Ma and U. Sarkar, Phys. Rev. Lett. 80, 5716 (1998). [9] G. B. Gelmini and M. Roncadelli, Phys. Lett. B99, 411 (1981). [10] N. Arkani-Hamed and S. Dimopoulos, hep-ph/9811353. [11] H. N. Brown et al., Phys. Rev. Lett. 86, 2227 (2001). [12] A. Czarnecki and W. J. Marciano, Phys. Rev. D64, 013014 (2001); other estimates of the possible discrepancy include J. Erler and M. Luo, Phys. Rev. Lett. 87, 071804 (2001); F. J. Yndurain, hep-ph/0102312; S. Narison, Phys. Lett. B513, 53 (2001); F. Jegerlehner, hep-ph/0104304; K. Melnikov, hep-ph/0105267. [13] E. Ma, Phys. Lett. B516, 165 (2001). [14] E. Ma, hep-ph/0107177 (Phys. Rev. D64, in press).


Doublet model BR

Figure 1: Lower bounds on B(τ → ?γ), B(? → eγ), and R?e .



Verifiable Origin of Neutrino Mass at TeV Scale.pdf

Verifiable Origin of Neutrino Mass at TeV Scale_专业资料。The physics responsible for neutrino mass may reside at or below the TeV energy scale. The ...

Particle Physics_图文.ppt

To understand the origin and destiny of the ...2000: direct evidence for tau neutrino (??) at...WX pp?tt [TeV] [kHz] [ns] 10 Run I 1.8 ...

Neutrino Mass, Dark Matter, and Leptogenesis.pdf

origin of neutrino mass, thereby linking inexorably two undisputed (and ...Leptogenesis at the TeV scale may also be possible, as well as a ...

Neutrino masses and electroweak symmetry breaking.pdf

nature of electroweak symmetry breaking and the origin of neutrino masses. ...scale neutrino mass models which can be made natural up to few TeV or ...

Revelations of the E_6U(1)_N Model Two-Loop Neutrino Mass and....pdf

the important new idea that dark matter is the origin of neutrino mass....At the TeV energy scale, this model predicts a new ZN gauge boson, ...

Beyond the Standard Model in the Lepton Sector.pdf

If supersymmetry exists at the TeV scale it ...Nobody knows the origin of this R parity ...Theories and the Physics of Neutrino Mass, Prog....

Supernova-Remnant Origin of Cosmic Rays_图文.pdf

Supernova-Remnant Origin of Cosmic Rays_专业资料... TeV and neutrino telescopes will also be ...The color-scale indicates the intensity of CO(J...

Relating leptogenesis and dark matter.pdf

a possible mechanism for the origin of the ...TeV states and yet they must be quite narrow, ... the mass scale comes in naturally, the draw...

Study of Active Galactic Nuclei at TeV Energies with ....pdf

Variability on a time scale of hours has been observed at TeV energies 10...The -radiation originates in these jets. Radio observations indicate that ...

Observation of the giant radio galaxy M87 at TeV energies ....pdf

? 40? . The mass of the black hole in the ... the TeV γ-ray production in large scale jets...origin of cosmic rays”, Pergamon Press, Oxford ...

May, 1997 50 TeV HEGRA Sources and Infrared Radiation.pdf

If the intrinsic ?ux has its origin in the ...(2) where me is the electron mass, εc is ...TeV both the neutrino-nucleon cross section and ...

Cerenkov's Effect and Neutrino Oscillations in Loop Quantum ....pdf

Bounds on the scale parameter {\cal L} arising...(GZK) limit anomaly and to the so called TeV-... cosmic rays have extragalactic origin [1214]...

Neutrinos from Gamma Ray Bursts.pdf

gamma ray burst requires a kilometer-scale ...a measurement of the neutrino mass to order 10?...initiated by TeV gamma rays 9] of GRB origin....

Electroweak-Scale Resonant Leptogenesis.pdf

Sneutrino Leptogenesis a... 暂无评价 13页 免费 TeV scale resonant lepto... 98.80.Cq 1 1 Introduction The origin of the baryon asymmetry in our ...

Phenomenology of neutrino physics in the Kaluza-Klein ....pdf

theory that originates from the non-observation ...mass scales) are generated by the physics of ...TeV from non-universal couplings of the neutrinos...

The Extragalactic Neutrino Background Radiations From Blazars....pdf

The Extragalactic Neutrino Background Radiations ...trace the origin of the extragalactic di use ...If the TeV gamma rays are produced by pion ...

Flux of upward high-energy muons at the multi-component ....pdf

component model of primary cosmic ray origin 2 E...Atmospheric neutrino (anti-neutrino) energy spectra... where ΦA is a scale factor (E in TeV ...

Neutrino Absorption Tomography of the Earth's Inter....pdf

10000 TeV to study the interior structure of ...km3 -scale neutrino telescope can be inverted to...with ultra-high energy neutrinos of cosmic origin...

Signals For Extra Dimensions at the VLHC.pdf

nely-spaced in mass; (ii) those with TeV-scale dimensions(TeV)[2], ...dominance of spin-2 exchange thus nailing down the gravitational origin of ...

Searches for the Supersymmetric Partner of the Bottom Quark_....pdf

center-of-mass energy of s = 1.96 TeV was ...decays in which / the neutrino escapes detection....The ET in signal originates form the neutralinos...

网站首页 | 网站地图
All rights reserved Powered by 酷我资料网 koorio.com
copyright ©right 2014-2019。