Search for New Physics at the Milliscale

Transcription

1 Search for New Physics at the Milliscale Andreas Ringwald DESY Seminar, University of Graz, 26 November 2008, Graz, A

2 Search for New Physics at the Milliscale 1 1. Introduction Hints for new particles beyond standard model: Light neutrino masses: new heavy neutrinos Unification of forces: heavy superpartners Strong CP problem: ultralight axion Dark matter: lightest superpartner or ultralight axion Dark energy: ultralight acceleron ν L ν L 1/Λ = h 0 h 0 ν L h ν ν R 1/M R ν L h ν h 0 h 0

3 Search for New Physics at the Milliscale 2 1. Introduction Hints for new particles beyond standard model: Light neutrino masses: new heavy neutrinos Unification of forces: heavy superpartners Strong CP problem: ultralight axion Dark matter: lightest superpartner or ultralight axion Dark energy: ultralight acceleron 1/α i Unification of the Coupling Constants in the SM and the minimal MSSM log Q 1/α i /α 1 1/α 2 1/α 3 MSSM [Amaldi, de Boer, Fürstenau 91] 10 log Q

4 Search for New Physics at the Milliscale 3 1. Introduction Hints for new particles beyond standard model: Light neutrino masses: new heavy neutrinos Unification of forces: heavy superpartners Strong CP problem: ultralight axion Dark matter: lightest superpartner or ultralight axion Dark energy: ultralight acceleron a g g

5 Search for New Physics at the Milliscale 4 1. Introduction Hints for new particles beyond standard model: Light neutrino masses: new heavy neutrinos Unification of forces: heavy superpartners Strong CP problem: ultralight axion Dark matter: lightest superpartner or ultralight axion Dark energy: ultralight acceleron

6 Search for New Physics at the Milliscale 5 Heavy superpartners of standard model particles as well as ultralight axion may easily be accommodated in Grand Unified Theories and occur especially naturally in the low-energy description of string theory Phenomenologically viable string compactifications potentially predict even more Weakly Interacting Sub-eV Particles (WISPs): Axion-Like Particles (ALPs) hidden-sector U(1) gauge bosons ( hidden photons) hidden-sector U(1) charged fermions ( minicharged particles)

7 Search for New Physics at the Milliscale 6 Physics at the Terascale: The Large Hadron Collider (LHC) has a huge discovery potential for WIMPs Physics at the Milliscale: Experiments exploiting lowenergy photons and/or large electromagnetic fields have considerable discovery potential for WISPs

8 Search for New Physics at the Milliscale 7 Physics at the Terascale: The Large Hadron Collider (LHC) has a huge discovery potential for WIMPs Searching for missing E T : Physics at the Milliscale: Experiments exploiting lowenergy photons and/or large electromagnetic fields have considerable discovery potential for WISPs

9 Search for New Physics at the Milliscale 8 Physics at the Terascale: The Large Hadron Collider (LHC) has a huge discovery potential for WIMPs Physics at the Milliscale: Experiments exploiting lowenergy photons and/or large electromagnetic fields have considerable discovery potential for WISPs

10 Search for New Physics at the Milliscale 9 Physics at the Terascale: The Large Hadron Collider (LHC) has a huge discovery potential for WIMPs Physics at the Milliscale: Experiments exploiting lowenergy photons and/or large electromagnetic fields have considerable discovery potential for WISPs Searching for light shining through a wall: [Ahlers (unpubl.)]

11 Search for New Physics at the Milliscale 10 Outline: 2. Axions and Axion-Like Particles 3. Ultralight Hidden-Sector Particles 4. Light Shining Through a Wall 5. Microwave Cavity Experiments 6. Conclusions

12 Search for New Physics at the Milliscale Axions and Axion-Like Particles Strong CP problem: Due to non-abelian nature of QCD, additional CP-violating term in the Lagrangian, L CP viol. = α s 4π θ trg µν G µν α s 4π θ 1 2 ǫµναβ trg µν G αβ Effective CP-violating parameter in standard model, θ θ = θ + arg det M Upper bound on electric dipole moment of neutron θ Unnaturally small!

13 Search for New Physics at the Milliscale 12 Peccei-Quinn solution to the strong CP problem: Introduce global anomalous chiral U(1) PQ symmetry, spontaneously broken by the vev of a complex scalar Φ = f a e ia/f a [Peccei,Quinn 77] Axion field a shifts under a U(1) PQ transformation, a a + const. Axion field can enter in Lagrangian only through derivative terms and explicit symmetry violating terms originating from chiral anomalies, L a = 1 2 µa µ a + L int a [ ] µ a ; ψ f a + rα s 4πf a atrg µν G µν + sα 8πf a a F µν F µν +... θ-term in L SM +L a can be eliminated by exploiting the shift symmetry, a a θf a /r Topological charge density trg µν Gµν 0 provides nontrivial potential for axion field axion is pseudo-nambu-goldstone boson [S.Weinberg 78; Wilczek 78]

14 Search for New Physics at the Milliscale 13 Mass obtained via chiral perturbation theory: [S.Weinberg 78] m a = r m πf π f a mu m d m u + m d 0.6 mev For large f a : axion is ultralight and invisible: e.g. coupling to photons, ( ) GeV f a /r [J.E. Kim 79; Shifman et al. 80; Dine et al. 81;...] L aγγ = 1 4 g a F µν F µν = g a E B, with [Bardeen,Tye 78; Kaplan 85; Srednicki 85] g = rα 2πf a ( 2 3 m u + 4m d s ) m u + m d r ( GeV 1 10 ) GeV f a /r

15 Search for New Physics at the Milliscale 14 Generic prediction for axion:

16 Search for New Physics at the Milliscale 15 Axions in string theory: Axions with global anomalous PQ symmetries generic in string compactifications Model-independent axion of weakly coupled heterotic string: dual of B µν, with µ and ν tangent to 4d Minkowski spacetime: f a = g 2 s 2πV6 M 2 s GeV = α CM P 2π 2 Heterotic string: 10d low-energy Lagrangian: L 10d = 2πM8 s g 2 s 2πg 2 s Ô gr M 6 s 1 4 trf F 2πM4 s g 2 s Compactify 6 extra dimensions: L 4d = M2 P 2 Ô Ô 1 gr gtrf 4g YM 2 µνf µν 1 fa 2 Read off coefficients: 1 2 H H H H+... m a 10 9 ev MP 2 = 4π gs 2 Ms 8 V 6 ; g2 YM = 4πg2 s Ms 6V ; fa 2 = gs 2 6 2πMs 4V 6 Large M s = α YM /(4π) M P

17 Search for New Physics at the Milliscale 16 Axions in string theory: Axions with global anomalous PQ symmetries generic in string compactifications Axions in intersecting D-brane models in type II string theory come from zero modes of the RR gauge fields C f a M s wider range of possibilities; phenomenologically preferred: intermediate scale, M s M EW M P GeV m a 10 4 ev Intersecting D-brane models: Gauge theory lives on D(3 + q)- branes, extending along the 4 noncompact dimensions and wrapping a q-cycle in the extra dimensions Gravity lives in all 10 dimensions Observable Brane Higher dimensional Bulk Smaller string scale because of large volume, M s g s M P / Ô V 6 M 6 s ; can be as low as TeV

18 Search for New Physics at the Milliscale 17 Axion-like particles: Other (pseudo-)nambu-goldstone bosons associated with breakdown of other continuous global symmetries Familons, associated with global family symmetry [Wilczek 82] Majorons, associated with global U(1) B L [Chikashige,Mohapatra,Peccei 80] Accelerons: [Friemann,Hill,Stebbins,Waga 95] breaking scale f φ M P and explicit symmetry breaking scale Λ m ν 10 3 ev m φ Λ 2 /f φ ev H 0 Stückelberg axions: associated with anomalous U(1)s in low-scale string compactifications [Coriano,Irges,Kiritsis 06]... Not as predictive as axion: explicit symmetry breaking scale? any experimental hint from astrophysics, cosmology, and laboratory experiments very welcome

19 Search for New Physics at the Milliscale 18 Constraints on axion-like particles: [Raffelt;...] HB stars Galactic dark matter Photon regeneration due to ALP-γ oscillations (light shining through a wall; CERN Axion Solar Telescope (CAST); galactic dark matter search); energy loss (lifetime of Helium Burning (HB) stars);

20 Search for New Physics at the Milliscale Ultralight Hidden-Sector Particles Most extensions of standard model based on supergravity or superstrings predict hidden sector of particles which are very weakly coupled to the visible sector standard model particles cf. gravity mediation of SUSY breaking from hidden sector to visible sector Gauge interactions in hidden sector generically involve U(1) factors. There are also hidden sector matter particles charged under these U(1)s. Usual assumption: hidden sector particles very heavy no constraints from low-energy phenomenology Here: what if hidden sector particles remain massless or light? hidden sector U(1) gauge boson ( hidden photon γ ) interacts with visible photon through gauge kinetic mixing hidden sector U(1) charged matter appears to have a small electric charge due to this mixing ( minicharged particle ǫ)

21 Search for New Physics at the Milliscale 20 Simplest model: [Holdom 85] L = 1 4 F µν F µν }{{} U(1) visible 1 4 Bµν B µν }{{} U(1) hidden χ F µν B µν }{{} kinetic mixing Dimensionless kinetic mixing parameter χ: + v(i / + ea/)v }{{} visible matter + h(i / + e h B/)h }{{} hidden matter Kinetic mixing generically appears in theories with several U(1) factors (renormalizable term respecting gauge and Lorentz symmetry) Integrating out heavy particles generically tends to generate χ 0: χ = ee h 16π 2 log(m 2 /µ 2 )

22 Search for New Physics at the Milliscale 21 Diagonalization of kinetic term: B µ B µ + χa µ U(1) visible unaffected, up to renormalization, e 2 e 2 /(1 χ 2 ) Hidden sector charged particle gets induced electric charge: e h hb/h eh h B/ h + χeh ha/ h Q vis h ǫe = χe h may be fractional may be tiny, if χ 1: h is minicharged particle Possible parameter ranges in string phenomenology: [Dienes et al. 97; Abel et al. 08] χ ; m γ 0 M s ; m ǫ 0 M s

23 Search for New Physics at the Milliscale 22 U(1) factors in hidden sectors: generic prediction of realistic string compactifications E 8 E 8 heterotic closed string theory IIA/IIB open string theory with branes Orbifold compactifications of heterotic string theory: e.g. [Buchmüller et al. 07;... ] E 8 E 8 G SM U(1) 4 SU(4) SU(2) U(1) 4 Some hidden U(1) gauge bosons and hidden charged fermions may remain massless or light Dominant interaction with standard model: gauge kinetic mixing and minicharge or [Lebedev et al. 07] E 8 E 8 G SM U(1) 4 SO(8) SU(2) U(1) 3 and many more

24 Search for New Physics at the Milliscale 23 U(1) factors in hidden sectors: generic prediction of realistic string compactifications E 8 E 8 heterotic closed string theory IIA/IIB open string theory with branes Some hidden U(1) gauge bosons and hidden charged fermions may remain massless or light Dominant interaction with standard model: gauge kinetic mixing and minicharge Compactification of type II string theory: Hidden Sectors CY 3 M 4 U(3) Q L Q R U(2) U(1) e L e R U(1) Visible Sector (SM)

25 Search for New Physics at the Milliscale 24 U(1) factors in hidden sectors: generic prediction of realistic string compactifications E 8 E 8 heterotic closed string theory IIA/IIB open string theory with branes Favored mass scales for hidden U(1)s: [...; Antoniadis et al. 02] 0 M2 s M P m γ M s Some hidden U(1) gauge bosons and hidden charged fermions may remain massless or light Dominant interaction with standard model: gauge kinetic mixing and minicharge In particular, for M s TeV, 0 mev m γ TeV

26 Search for New Physics at the Milliscale 25 U(1) factors in hidden sectors: generic prediction of realistic string compactifications KM in heterotic string models: [Dienes,Kolda,March-Russell 97] E 8 E 8 heterotic closed string theory IIA/IIB open string theory with branes Some hidden U(1) gauge bosons and hidden charged fermions may remain massless or light µ Va χ ee h 16π 2 C m M P ν Vb Dominant interaction with standard model: gauge kinetic mixing and minicharge > 10 17, for C > 10, m> 100 TeV

27 Search for New Physics at the Milliscale 26 U(1) factors in hidden sectors: generic prediction of realistic string compactifications E 8 E 8 heterotic closed string theory IIA/IIB open string theory with branes KM in IIA/IIB string models: [Lüst,Stieberger 03;Abel,Schofield 04;Berg,Haack,Körs 05] Some hidden U(1) gauge bosons and hidden charged fermions may remain massless or light Dominant interaction with standard model: gauge kinetic mixing and minicharge χ e e h ( ) V6 16π 2 Ms 6 2/3 > 10 23, for V 6 M 6 s < 1030 (i.e. M s > TeV)

28 Search for New Physics at the Milliscale 27 Constraints on hidden photons: [Bartlett,.. 88; Kumar,.. 06; Ahlers,.. 07; Jaeckel,.. 07; Redondo,.. 08] Deviations from 1/r 2 (Coulomb); γ γ oscillations (Cavity, Light Shining through a Wall (LSW), Sun); Z γ mixing (LEP, LHC, ILC)

29 Search for New Physics at the Milliscale 28 Constraints on minicharged particles: [Davidson,.. 90;Gies,.. 06;Ahlers,.. 07;Melchiorri,.. 07] Energy loss (Red Giants, RF Cavity); cosmic expansion rate (BBN); deviations of black body spectrum (CMB); γ γ oscillations (LSW);...

30 Search for New Physics at the Milliscale Light Shining through a Wall Linearly polarized laser beam in vacuum or along a transverse magnetic field Place wall in beam pipe: LSW via γ-γ oscillations: γ γ γ γ laser beam will be absorbed neutral WISPs (γ, ALP) fly through wall and reconvert on other side of wall into photons, which can be detected [Okun 82;Sikivie 83;Anselm 85;..] photon-alp oscillations: Pioneering experiment: BFRT γ laser φ γ laser Several ongoing experiments B B

31 Search for New Physics at the Milliscale Light Shining through a Wall Linearly polarized laser beam in vacuum or along a transverse magnetic field Place wall in beam pipe: laser beam will be absorbed neutral WISPs (ALP, γ ) fly through wall and reconvert on other side of wall into photons, which can be detected [Okun 82;Sikivie 83;Anselm 85;..] Pioneering experiment: BFRT Several ongoing experiments Experiment Laser Cavity Magnets ALPS 532 nm; kw BFRT 500 nm; 3 W Np = 200 BMV γ/pulse GammeV 532 nm; 3.2 W LIPSS 900 nm; 3 kw B 1 = B 2 = 5 T l 1 = l 2 = 4.21 m B 1 = B 2 = 3.7 T l 1 = l 2 = 4.4 m B 1 = B 2 = 11 T l 1 = l 2 = 0.25 m B 1 = B 2 = 5 T l 1 = l 2 = 3 m B 1 = B 2 = 1.7 T l 1 = l 2 = 1 m OSQAR 1064 nm; 1 kw Np 10 4 B 1 = B 2 = 9.5 T l 1 = l 2 = 7 m

32 Search for New Physics at the Milliscale Light Shining through a Wall Linearly polarized laser beam in vacuum or along a transverse magnetic field Any-Light Particle Search: [AEI, DESY, Hamburger Sternwarte, Laser Zentrum Hannover] Place wall in beam pipe: laser beam will be absorbed neutral WISPs (ALP, γ ) fly through wall and reconvert on other side of wall into photons, which can be detected [Okun 82;Sikivie 83;Anselm 85;..] Pioneering experiment: BFRT Several ongoing experiments

33 Search for New Physics at the Milliscale Light Shining through a Wall Linearly polarized laser beam in vacuum or along a transverse magnetic field Any-Light Particle Search: [AEI, DESY, Hamburger Sternwarte, Laser Zentrum Hannover] Place wall in beam pipe: laser beam will be absorbed neutral WISPs (ALP, γ ) fly through wall and reconvert on other side of wall into photons, which can be detected [Okun 82;Sikivie 83;Anselm 85;..] Pioneering experiment: BFRT Several ongoing experiments

34 Search for New Physics at the Milliscale Light Shining through a Wall Linearly polarized laser beam in vacuum or along a transverse magnetic field Place wall in beam pipe: laser beam will be absorbed neutral WISPs (γ, ALP) fly through wall and reconvert on other side of wall into photons, which can be detected [Okun 82;Sikivie 83;Anselm 85;..] Vacuum LSW: Limit on hidden γ Χ Coulomb x Planck FIRAS LSW Cavity ALPS Sun N Ν eff Pioneering experiment: BFRT Several ongoing experiments m Γ' ev [Jaeckel,Redondo,AR 08]

35 Search for New Physics at the Milliscale Light Shining through a Wall Linearly polarized laser beam in vacuum or along a transverse magnetic field Place wall in beam pipe: B 0 LSW: Limit on ALP laser beam will be absorbed neutral WISPs (ALP, γ ) fly through wall and reconvert on other side of wall into photons, which can be detected [Okun 82;Sikivie 83;Anselm 85;..] Pioneering experiment: BFRT Several ongoing experiments g GeV m ev ALPS (14 W (prel.),0.3 kw (proj.),10 kw (proj.)); BFRT; GammeV (- - -); OSQAR (prel.,proj.)

36 Search for New Physics at the Milliscale 35 Constraints on ALPs: Galactic dark matter

37 Search for New Physics at the Milliscale Microwave Cavity Experiments High quality cavities can be exploited to search for γ ALPs [Jaeckel,AR 07] Microwaves permeating through a shielding: substantial reach in parameter space for γ may reach CAST s ALPs sensitivity with presently available technology [Jaeckel,AR 07]

38 Search for New Physics at the Milliscale Microwave Cavity Experiments High quality cavities can be exploited to search for [Jaeckel,AR 07] γ ALPs [Hoogeveen 92] Microwaves permeating through a shielding: substantial reach in parameter space for γ may reach CAST s ALPs sensitivity with presently available technology [Jaeckel,AR 07]

39 Search for New Physics at the Milliscale Microwave Cavity Experiments High quality cavities can be exploited to search for γ ALPs [Jaeckel,AR 07] Microwaves permeating through a shielding: substantial reach in parameter space for γ may reach g GeV 1 with presently available technology [Jaeckel,AR 07]

40 Search for New Physics at the Milliscale Microwave Cavity Experiments Current-Through-a-Wall: In strong electric field of accelerator cavity, minicharged particles may be produced in pairs and accelerated along the beam axis MCP beam leaves cavity and is flowing through thick wall Corresponding electrical current can be measured directly via its induced magnetic field [Gies,Jaeckel,AR 06] E e crit = m2 e e 1018 V m Ecrit ǫ = m2 ǫ ǫe 5 MV m 10 6 ǫ ( mǫ mev Accelerator cavity: few 10 MV/m Focus of PW laser: few V/m ) 2

41 Search for New Physics at the Milliscale Microwave Cavity Experiments Current-Through-a-Wall: In strong electric field of accelerator cavity, minicharged particles may be produced in pairs and accelerated along the beam axis MCP beam leaves cavity and is flowing through thick wall Corresponding electrical current can be measured directly via its induced magnetic field [Gies,Jaeckel,AR 06] [Gies,Jaeckel,AR 06]

42 Search for New Physics at the Milliscale Microwave Cavity Experiments Current-Through-a-Wall: In strong electric field of accelerator cavity, minicharged particles may be produced in pairs and accelerated along the beam axis MCP beam leaves cavity and is flowing through thick wall Corresponding electrical current can be measured directly via its induced magnetic field [Gies,Jaeckel,AR 06] ACDC (Accelerator Cavity Dark Current): Cavity and wall available Measurement device available (in princ.) Sensitive probe of MCPs

43 Search for New Physics at the Milliscale Microwave Cavity Experiments Current-Through-a-Wall: In strong electric field of accelerator cavity, minicharged particles may be produced in pairs and accelerated along the beam axis MCP beam leaves cavity and is flowing through thick wall Corresponding electrical current can be measured directly via its induced magnetic field [Gies,Jaeckel,AR 06] ACDC (Accelerator Cavity Dark Current): Cavity and wall available Measurement device available Sensitive probe of MCPs

44 Search for New Physics at the Milliscale Microwave Cavity Experiments Current-Through-a-Wall: In strong electric field of accelerator cavity, minicharged particles may be produced in pairs and accelerated along the beam axis MCP beam leaves cavity and is flowing through thick wall Corresponding electrical current can be measured directly via its induced magnetic field ACDC (Accelerator Cavity Dark Current): [Gies,Jaeckel,AR 06] [Gies,Jaeckel,AR 06] Cavity and wall available Measurement device available Sensitive probe of MCPs

45 Search for New Physics at the Milliscale Microwave Cavity Experiments Current-Through-a-Wall: In strong electric field of accelerator cavity, minicharged particles may be produced in pairs and accelerated along the beam axis MCP beam leaves cavity and is flowing through thick wall Corresponding electrical current can be measured directly via its induced magnetic field ACDC (Accelerator Cavity Dark Current): [Gies,Jaeckel,AR 06] Cavity and wall available Measurement device available (in princ.) Sensitive probe of MCPs

46 Search for New Physics at the Milliscale Microwave Cavity Experiments Current-Through-a-Wall: In strong electric field of accelerator cavity, minicharged particles may be produced in pairs and accelerated along the beam axis MCP beam leaves cavity and is flowing through thick wall Corresponding electrical current can be measured directly via its induced magnetic field ACDC (Accelerator Cavity Dark Current): [Gies,Jaeckel,AR 06] Cavity and wall available Measurement device available (in princ.) Sensitive probe of MCPs

47 Search for New Physics at the Milliscale Microwave Cavity Experiments Current-Through-a-Wall: In strong electric field of accelerator cavity, minicharged particles may be produced in pairs and accelerated along the beam axis MCP beam leaves cavity and is flowing through thick wall Corresponding electrical current can be measured directly via its induced magnetic field [Gies,Jaeckel,AR 06] ACDC (Accelerator Cavity Dark Current): Cavity and wall available Measurement device available (in princ.) Sensitive probe of MCPs

48 Search for New Physics at the Milliscale Microwave Cavity Experiments Current-Through-a-Wall: In strong electric field of accelerator cavity, minicharged particles may be produced in pairs and accelerated along the beam axis MCP beam leaves cavity and is flowing through thick wall Corresponding electrical current can be measured directly via its induced magnetic field [Gies,Jaeckel,AR 06] ACDC (Accelerator Cavity Dark Current): log 10 ǫ µa na [Ahlers,Gies,Jaeckel,AR in prep.] log 10 m ǫ [ev]

49 Search for New Physics at the Milliscale Conclusions A low-energy frontier is forming worldwide: Fundamental physics with low energy photons and spare parts from high-energy frontier accelerators These laboratory experiments have considerable discovery potential for ultralight particles beyond the standard model, which appear quite naturally in realistic string compactifications: axion-like particles hidden-sector U(1) gauge bosons hidden-sector fermions charged under these extra U(1)s Theoretical predictions of masses and couplings very uncertain any experimental hint or constraint extremely welcome!

50 Search for New Physics at the Milliscale 49 In contrast to a WIMP: If a WISP is found, it may have immediate applications WISP beam radio!