Search for Lμ-Lτ gauge boson at Belle-II

Transcription

1 Search for Lμ-Lτ gauge boson at Belle-II Takashi Shimomura (Miyazaki U.) in collaboration with Yuya Kaneta (Niigata U.) On the possibility of search for Lμ Lτ gauge boson at Belle-II and neutrino beam experiments and T. Araki, S. Hoshino, J. Sato, T. Ota (Saitama U.) Detecting the Lμ Lτ gauge boson at Belle-II arxiv: , PTEP arxiv: , PRD November 1st, Flavor Physics Workshop

2 Introduction The standard model has been completed by the discovery of the Higgs particle. However, Neutrino mass and mixing Dark matter / Dark energy muon (g-2) etc Need new physics beyond the SM No good news from LHC so far. No SUSY, No extra dim. Where is new physics? Further high energy scale? Low scale but unexpectedly hidden?

3 Light and Weakly interacting gauge boson IceCube resonant absorption of cosmic ν cos C B M Z 0 Z 0 ' p 2E m ' O(10) MeV cos C B Eν = 1 PeV, mν = 0.1 ev JN 09 (e + e -based) 301 ± 65 DHMZ 10 (τ-based) 197 ± 54 DHMZ 10 (e + e ) 289 ± 49 HLMNT 11 (e + e ) 263 ± 49 BNL-E821 (world average) 0 ± 63 (g-2)μ BNL-E IPCC (relative unit) exp 10 a µ a 11 µ a µ new int. with muon Z 0 µ µ For mz mμand g =10-4 a µ ' g ' O(10 9 ) Atomki m 0 c 2 =15.6 MeV m 0 c 2 =16.6 MeV m 0 c 2 =17.6 MeV Θ (deg.) m Z 0 decay into e + e - Be best fit Z 0 e e + Be = MeV

4 Light and Weakly interacting gauge boson IceCube resonant absorption of cosmic ν cos C B M Z 0 Z 0 JN 09 (e + e -based) 301 ± 65 DHMZ 10 (τ-based) 197 ± 54 DHMZ 10 (e + e ) 289 ± 49 HLMNT 11 (e + e ) 263 ± 49 BNL-E821 (world average) 0 ± 63 (g-2)μ BNL-E ' p 2E m ' O(10) MeV cos C B Eν = 1 PeV, mν = 0.1 ev IPCC (relative unit) exp 10 a µ a 11 µ a µ new int. with muon Z 0 µ µ For mz mμand g =10-4 a µ ' g ' O(10 9 ) Atomki m 0 c 2 =15.6 MeV m 0 c 2 =16.6 MeV m 0 c 2 =17.6 MeV Θ (deg.) m Z 0 decay into e + e - Be best fit Z 0 e e + Be = MeV

5 Purpose How can we search for such a light and weakly int. gauge boson? Need high statistics due to the weak int. Low energy beam enough to produce. Clear signal to discriminate from the SM BG. Belle-II experiment e + -e - collider with the total luminosity = 50 ab -1. the c.m. energy = GeV Low BG from the weak int. One photon + Missing event search.

6 Lμ Lτ

7 Gauged U(1)Lμ-Lτ model A minimal extension of the SM Anomaly free Large neutrino mixing (approx.) Choubey, Rodejohann, Eur.Phys.J, (2005) Ota, Rodejohann, Phys.Lett. (2006) Asai, Hamaguchi, Nagata, The Lagrangian He, Joshi, Lew, Volkas, PRD (1991), R. Foot, Mod.Phys.Lett. (1991) l e e R l µ µ R l R L µ L Kinetic mixing with SM gauge boson L new = 1 4 Z0 µ Z 0µ + m2 Z 0 2 Z0 µz 0µ + 2 B µ Z 0µ +g 0 Z 0 µ ( µ µ µ + µ µ µ µ µ ) new interactions for μ, τ and ν Simple model Only one new particle, Z, is introduced. Three extra parameters (mz, g and ε) are added. * The scalar sector is not specified.

8 Gauge interactions In mass basis, the gauge int. is given as L int = Z 0 µ e cos W J µ EM + g0 J µ Z 0 + O( 2 ) where J µ EM = 2 3ū µ u J µ Z d µ d ē µ e +, = µ µ µ + µ µ µ µ µ, Z 0 B ecos W J EM

9 Gauge interactions In mass basis, the gauge int. is given as L int = Z 0 µ e cos W J µ EM + g0 J µ Z 0 + O( 2 ) where J µ EM = 2 3ū µ u J µ Z d µ d ē µ e +, = µ µ µ + µ µ µ µ µ, Z 0 e e cos W Z 0 e + µ / ±g 0 e cos W µ + / + Z 0 e The coupling can be enhanced or suppressed e No constraints from reactor exp.

10 Allowed Parameter Space MZ =10 MeV and ε > 0 Meson decay ν-e scattering Beam dump Trident 2σ 3σ

11 Allowed Parameter Space MZ =10 MeV and ε > 0 cancellation due to g 0 e cos W Meson decay dark photon like ν-e scattering Beam dump pure Lμ-Lτ Trident

12 Allowed Parameter Space MZ =10 MeV and ε < 0 Meson decay No cancellation ν-e scattering Beam dump Trident

13 MZ =50 MeV Meson decay Beam dump MZ =100 MeV

14 Loop-induced Kinetic Mixing Even if the tree-level kinetic mixing is zero, it is generated at a loop level, Z 0 q µ/ q = 8eg0 (4 ) 2 Z 1 0 x(1 x)ln m2 x(1 x)q 2 m 2 µ x(1 x)q 2 dx Heavy Light momentum dependence Μ Ζ [GeV] q 2 = M 2 Z mass dependence ε = constant (Eq. (6)) q 2 = 0 ε g =10-3 ε = Π(Μ Ζ 2 ) (Our model) In the CM frame s = GeV g Z = Ε γ [GeV] Larger for smaller mz Not negligible

15 Allowed Parameter Space Loop-induced kinetic mixing case

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17 One-Photon + Missing The SM process e + e! Z! e New process e + Z e + e! Z 0 Z 0! suppressed due to heavy Z/W mass 3-body final state e e + Z 0 g 0 Z 0 2-body final state

18 diff. Cross Section at Belle-II mz = 100 MeV

19 diff. Cross Section at Belle-II 1-photon (Eγ >5 GeV)+ missing events mz = 100 MeV > 5GeV ~10 event SM a few event

20 σ Br(Z Belle-II MZ =10 MeV and ε > 0 a µ = a µ = events 10 3 events 10 2 events 10 events 1 events 2σ 3σ

21 σ Br(Z Belle-II MZ =10 MeV and ε > 0 σ Br g 2 Br / 2 g02 g events σ Br ε events 10 2 events 10 events 1 events 2σ 3σ

22 σ Br(Z Belle-II MZ =10 MeV and ε > 0 More than 100 events 10 4 events 10 3 events g 0, > events 10 events 1 events 2σ 3σ

23 σ Br(Z Belle-II MZ =10 MeV and ε < 0 More than 100 events 10 4 events 10 3 events g 0, > events 10 events 1 events 2σ 3σ

24 MZ =50 MeV a µ = a µ = MZ =100 MeV

25 Loop-induced kinetic mixing For the light gauge boson, 10 2 g 0 g > signal significance S > 3 S N sig(g Z 0,M Z 0) p NBG

26 Summary Motivated by IceCub and (g-2)μ, weakly int. gauge boson with MeV-scale mass was studied in the gauged Lμ-Lτ model. Allowed region of the parameter space was shown for different masses. One-photon + missing cross section at Belle-II is large enough in the region with g & ε > Future work Multi-photon final states are also serious BG. e + + e - γ + missing

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28 Back-Up

29 IceCube Gap IceCube has observed high Energy Neutrinos IceCube, PRL. 113 (2014) No(less) Events observed A gap in the flux between 400TeV(700TeV)-1PeV Astrophysical origin e.g. two different sources Particle physics origin Attenuation of the cosmic ν

30 IceCube Gap Attenuation of the cosmic ν Introduce a new gauge/scalar boson which interacts with neutrinos. cos p Ioka and Murase, PTEP 2014, Ng and Beacom, PRD90 (2014), Ibe and Kaneta, PRD90 (2014) Araki, Kaneko, Konishi, Ota, Sato, T.S., PRD91 (2015) Araki, Kaneko, Ota, Sato, T.S., PRD93 (2016) C B g 0 g 0 Z : Lμ-Lτ gauge boson Z 0 g : gauge coupling At the resonant, the scattering cross section is enhanced. The cosmic ν is attenuated by the cosmic ν BG. For the IceCube gap energy (1 PeV), q m Z 0 = p 2 ' p 2m E ' 10 MeV Very light gauge boson

31 IceCube Gap Araki, Kaneko, Konishi, Ota, Sato, T.S., PRD91 (2015) Araki, Kaneko, Ota, Sato, T.S., PRD93 (2016) E ν 2 Φ [10-8 GeV cm -2 s -1 sr -1 ] Normal Hierarchy E ν [GeV] s ν =2.5 s ν =2.3 s ν =2.1 IceCube E ν 2 Φ [10-8 GeV cm -2 s -1 sr -1 ] Inverted Hierarchy E ν [GeV] s ν =2.3 s ν =2.1 IceCube mz = 11 MeV & g = mz = 9 MeV & g = The IceCube gap suggests Very light and Weakly interacting Gauge Boson

32 Atomki anomaly Excess of e + -e - pair from an excited state of 8 Be J. Feng, et al., PRD 95 (2017) 8 Be! 8 Be + e + + e Parity conserving transition M1 transition emitting a photon

33 Atomki anomaly Krasznahorkay, etal., PRL. 116 (2016), EPJ Web Conf. 137 (2017) Invariant mass of e + -e - Opening angle of e + -e - 6.8σ deviation from the standard nuclear interpretation The best fit is 17.0±0.5(stat)±0.5(sys) MeV The coupling const. should be O(10-4 ) J. Feng, et al. PRD 95 (2016), Zhang and Miller, , O. Seto and T.S, PRD (2017)

34 Muon (g-2) PDG (2014) JN 09 (e + e -based) 301 ± 65 DHMZ 10 (τ-based) 197 ± 54 DHMZ 10 (e + e ) 289 ± 49 HLMNT 11 (e + e ) 263 ± 49 BNL-E821 (world average) 0 ± 63 BNL-E world average theory prediction exp 10 a µ a 11 a µ µ a exp µ = ( (5.4)(3.3)) a SM µ = ( ± 4.9) K. Hagiwara et al, J.Phys. G38 (2011) a µ = 288(63)(49) σ discrepancy

35 Muon (g-2) Z contribution to (g-2)μ Z 0 µ µ a µ = g0 2 8 Z 1 0 2m 2 µ x(1 x)2 dx xm 2 Z +(1 x) 2 m 2 0 µ gauged Lμ-Lτ model BaBar excluded g 0 g-2 favored m Z 0 (MeV) Araki, Kaneko, Ota, Sato, T.S, PRD93 (2016)

36 Purpose Neutrino beam experiment Various on-going/future plan with high statistics. Neutrino beam energy of O(1-10) GeV. Neutrino Trident Production Search Altomannshofer, et al, PRL.113 (2014) µ µ Coulomb field µ µ 4 Fermi suppressed processes Nucleus/Nucleon Nucleus/Nucleon Study the possibility of detecting the Lμ-Lτ gauge boson at Belle-II and Neutrino beam exp.

37 Loop-induced Kinetic Mixing Even if the tree-level kinetic mixing is zero, it is generated at a loop level, Z 0 q µ/ q = 8eg0 (4 ) 2 Z 1 0 x(1 x)ln m2 x(1 x)q 2 m 2 µ x(1 x)q 2 dx Heavy Μ Ζ [GeV] Light momentum dependence q 2 = M 2 Z mass dependence ε = constant (Eq. (6)) q 2 = 0 ε ε = Π(Μ Ζ 2 ) (Our model) In the CM frame s = GeV g Z = g = Ε γ [GeV] Larger for smaller mz Not negligible

38 Constraints 1. Muon anomalous magnetic moment Z 0 µ µ a Z0 µ = (g0 e cos W ) Z 1 0 dx 2m 2 µ x2 (1 x) x 2 m 2 µ +(1 x)m2 Z 0, 12.8 (4.8) apple a Z0 µ apple 44.8 (3σ) 2. Neutrino trident production processes The scattering of a neutrino off a nuclei, producing muons Z 0 Nucleus µ µ R CCFR R CHARM II CCFR SM =0.82 ± 0.28 CHARM II SM =1.58 ± 0.75

39 Constraints e 3. Neutrino-Electron scattering Z 0 g e 2 3 3X 4( ecos W ) 2 f i g ij 2 5 j=1 1/4 e cos W g ij g 0 (V QV ) ij <g B L fi : mass eigenstates ratio at the Earth Hg-2L m U Atomic Physics Atomic Physics 10-2 gauge coupling gb-l CMB Gemma B-L Gauge Boson CMB LSW Fifth Force SunêGlobular Clusters, energy loss via n CAST Borexino A' capture in Sun Gauge boson mass M A' HGeVL Harnik, Kopp, Machado, JCAP 1207 (2012) Sun Globular Clusters Hg-2L e Fixed target SN1987A

40 Constraints e 3. Neutrino-Electron scattering Z 0 g 0 e 2 3 3X 4( ecos W ) 2 f i g ij 2 5 j= Hg-2L m U Atomic Physics 1/4 e cos W g ij g 0 (V QV ) ij 10-2 <g B L fi : mass eigenstates ratio at the Earth LSW CAST Borexino A' capture in Sun Hg-2L e Fixed target ers SN1987A Harnik, Kopp, Machado, JCAP 1207 (2012)

41 Constraints e 4. Beam dump experiment E774 DarkLight A' Æ Standard Model a m, 5 s VEPP-3 a m,±2 s favored a e WASA MESA E141 Essig, et al. arxiv: KLOE MAMI APEXêMAMI Test Runs APEX BaBar ε Meson decay (g 2) µ WASA e (g 2) (3σ) NA/48, PLB746 (2015) HADES KLOE A1 APEX Orsay HPS BaBar 10-5 U m A' HGeVL E774 E NA48/ m A 2 (MeV/c ) cos W p Br(Z0! e + e ) > BD q cos W Br(Z 0! e + e ) < MD

42 Constraints 6. e + -e - collider at BaBar ε (g-2) e Dark Photon Search BaBar, PRL113 (2014) WASA KLOE 2013 KLOE 2014 BABAR 2009 UL g' Lμ-Lτ Z Search BaBar, PRD94 (2016) Borexino Trident (g-2) ± µ 2σ favored HADES A1 APEX BABAR g-2 favored E774 E q cos W Br(Z 0! l + l (GeV) m A' ) < BaBar m Z' (GeV)

43 Neutrino beam exp. Neutrino Trident Production µ + N! µ + µ + µ + N ν beam energy dependence R E ν [GeV] R SM+Z0 SM 10 MeV 100 MeV CHARM-II CCFR

44 Neutrino beam exp. MZ =10 MeV and ε > Eν = 1.5 GeV 2σ can be explored with R=2 R CCFR =0.82 ±

45 Neutrino beam exp. MZ =10 MeV and ε < Eν = 1.5 GeV 2σ can be explored with R=2 R CCFR =0.82 ±