Light Paraphotons and Minicharged Particles in Realistic Extensions of the Standard Model

Transcription

1 Light Paraphotons and Minicharged Particles in Realistic Extensions of the Standard Model Andreas Ringwald DESY 3rd ILIAS-CERN-DESY Axion-WIMP Workshop June 23, 27 Patras, GR

2 Light Paraphotons and Minicharged Particles Introduction Most successful theory of all times: standard model Circumstantial evidence for existence of new particles beyond the standard model: Dark matter Unification of forces Neutrino masses Many extensions of the standard model predict not only very massive, often very short-lived new particles, but also very light and very long-lived ones A keyhole to hidden sectors of nature

3 Light Paraphotons and Minicharged Particles Introduction Most successful theory of all times: standard model Circumstantial evidence for existence of new particles beyond the standard model: Dark matter Unification of forces Neutrino masses Many extensions of the standard model predict not only very massive, often very short-lived new particles, but also very light and very long-lived ones A keyhole to hidden sectors of nature

4 Light Paraphotons and Minicharged Particles Introduction Most successful theory of all times: standard model Circumstantial evidence for existence of new particles beyond the standard model: Dark matter Unification of forces Neutrino masses Many extensions of the standard model predict not only very massive, often very short-lived new particles, but also very light and very long-lived ones A keyhole to hidden sectors of nature 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] 1 log Q

5 Light Paraphotons and Minicharged Particles Introduction Most successful theory of all times: standard model Circumstantial evidence for existence of new particles beyond the standard model: Dark matter Unification of forces Neutrino masses Many extensions of the standard model predict not only very massive, often very short-lived new particles, but also very light and very long-lived ones A keyhole to hidden sectors of nature

6 Light Paraphotons and Minicharged Particles Introduction Most successful theory of all times: standard model Circumstantial evidence for existence of new particles beyond the standard model: Dark matter Unification of forces Neutrino masses Many extensions of the standard model predict not only very massive, often very short-lived new particles, but also very light and very long-lived ones A keyhole to hidden sectors of nature [Ahlers (unpubl.)]

7 Light Paraphotons and Minicharged Particles Introduction Theoretically best motivated extensions of the standard model are based on string theory small strings in (9+1)-dimensional space-time are basic building blocks Unification of all forces, including gravitation Axion + Dilaton (S = a + ie φ ) Low-energy description in (3+1) dimensions: Particles of standard model + superpartners Hidden sector particles: light(?) paraphotons, para- (s)electrons,...

8 Light Paraphotons and Minicharged Particles Introduction Theoretically best motivated extensions of the standard model are based on string theory small strings in (9+1)-dimensional space-time are basic building blocks Unification of all forces, including gravitation Axion + Dilaton (S = a + ie φ ) Low-energy description in (3+1) dimensions: Particles of standard model + superpartners Hidden sector particles: light(?) paraphotons, para- (s)electrons,...

9 Light Paraphotons and Minicharged Particles Introduction Theoretically best motivated extensions of the standard model are based on string theory small strings in (9+1)-dimensional space-time are basic building blocks Unification of all forces, including gravitation Axion + Dilaton (S = a + ie φ ) Low-energy description in (3+1) dimensions: Particles of standard model + superpartners Hidden sector particles: light(?) paraphotons, para- (s)electrons,...

10 Light Paraphotons and Minicharged Particles Introduction Theoretically best motivated extensions of the standard model are based on string theory small strings in (9+1)-dimensional space-time are basic building blocks Unification of all forces, including gravitation Axion + Dilaton (S = a + ie φ ) Low-energy description in (3+1) dimensions: Particles of standard model + superpartners Hidden sector particles: light(?) paraphotons, para- (s)electrons,...

11 Light Paraphotons and Minicharged Particles Introduction Theoretically best motivated extensions of the standard model are based on string theory small strings in (9+1)-dimensional space-time are basic building blocks Unification of all forces, including gravitation Axion + Dilaton (S = a + ie φ ) Low-energy description in (3+1) dimensions: Particles of standard model + superpartners Hidden sector particles: light(?) paraphotons, para- (s)electrons,... [Ahlers (unpubl.)]

12 Light Paraphotons and Minicharged Particles Outline: 2. Paraphotons and Minicharged Particles Small mixing of hidden sector extra U(1) gauge bosons with the photon naturally leads to small visible electromagnetic charges of hidden sector extra particles 3. Gauge Kinetic Mixing in String Theory Extra U(1) gauge bosons and hidden sector extra particles occur naturally in embeddings of the standard model into string theory. 4. Summary

13 Light Paraphotons and Minicharged Particles Paraphotons and Minicharged Particles Minicharged particles arise very naturally in models with extra U(1) gauge bosons (paraphotons) [Okun 82; Holdom 85] Simplest model: L = 1 4 F µν F µν }{{} U(1) em 1 4 Bµν B µν }{{} U(1) hidden 1 2 χf µν B µν }{{} mixing Dimensionless mixing parameter χ χ = at high-energy scale χ generated by quantum fluctuations below this scale ( later)

14 Light Paraphotons and Minicharged Particles Diagonalization of kinetic term: B µ B µ χa µ U(1) em unaffected, up to multiplicative renormalization, e 2 e 2 /(1 χ 2 ) Hidden sector charged (e h ) particle gets induced electric charge: e h hb/h eh h B/ h χe h ha/ h Q h ǫe = χe h may be fractional may be tiny, if χ 1: minicharged particle Value of χ in well-motivated extensions of standard model?

15 Light Paraphotons and Minicharged Particles Gauge Kinetic Mixing in String Theory [Abel,Jaeckel,Khoze,AR 6] Most standard model extensions based on string theory predict additional U(1) factors Expected size of χ in particular string theory setting can be investigated by performing a oneloop calculation Het. SO(32) 11 D Sugra Type I Type IIA Weakly coupled heterotic closed string models Het. E8xE8 TypeIIB [Dienes,Kolda,March-Russell 97] Open string models involving stacks of Dirichlet branes and antibranes [Abel,Schofield 4] [Abel,Santiago 4]

16 Light Paraphotons and Minicharged Particles Gauge Kinetic Mixing in String Theory Heterotic string models: [Abel,Jaeckel,Khoze,AR 6] Most standard model extensions based on string theory predict additional U(1) factors Expected size of χ in particular string theory setting can be investigated by performing a oneloop calculation Weakly coupled heterotic closed string models [Dienes,Kolda,March-Russell 97] Open string models involving stacks of Dirichlet branes and antibranes [Abel,Schofield 4] µ Va IIA/IIB string models: ν Vb

17 Light Paraphotons and Minicharged Particles Heterotic string models: [Dienes,Kolda,March-Russell 97] µ Va ν Vb Kinetic mixing can be avoided by choosing vacua in which additional U(1)s are embedded into non-abelian structure Otherwise, nevertheless memory of original underlying non-abelian structure small, but nonzero χ Above string scale: kinetic mixing vanishes at LO Below string scale: kinetic mixing appears due to splitting of relevant matter multiplets, cf. contribution from two chiral superfields,

18 Light Paraphotons and Minicharged Particles (e, e h ) and (e, e h ), with masses m and m : χ ee ( ) h m 2 16π 2 log m 2 hidden sector Mass splittings m MSUSY (}{{} 1 4 GM 1 }{{} 11 ) GeV SUGRA χ (1 16 }{{} GM 1 9 }{{} SUGRA ) e h C }{{} 1 1 ( ) e h

19 Light Paraphotons and Minicharged Particles Open string models with D- and D-branes: IIB string models: [...;Aldazabal,Ibanez,Quevedo,Uranga ;...] Visible sector: stack of D3-branes at orbifold fixed point in internal space: u R Q L Hu g w b D3 d R E R D7 U(3) c L, H d U(2) L U(1)

20 Light Paraphotons and Minicharged Particles Hidden sector: D3-branes at other fixed points in the bulk: * * * * * * x SM x x * * * * * * 9 D7 18 D7 9 D Y = -1 1 Y1 = Y1 = +1 Y 3 Y 2 Y 1 IIA string models: [...;Blumenhagen,Görlich,Körs,Lüst ;...] Visible sector: D6-branes intersecting at non-trivial angles Hidden sector: D6-branes in the bulk

21 Light Paraphotons and Minicharged Particles... 2 Brane antibrane kinetic mixing: [Abel,Schofield 4] Stack of hidden sector antibranes carry U(1) factors Interact with visible sector branes by exchanging closed string modes: Cylinder diagram in closed string channel kinetic mixing diagram in open string channel:

22 Light Paraphotons and Minicharged Particles χ e e h V NN V DD,small (M s R) p d 7 e e h ( 2 (8 p)/2 α p M s M P ) 2(5 p) 6 p ( )d p+3 R 6 p r [Abel,Jaeckel,Khoze,AR 6]

23 Light Paraphotons and Minicharged Particles Hidden sector spectrum: Anomalous hidden sector U(1) gauge bosons have mass M s Non-anomalous hidden sector U(1) gauge bosons may be massless or light Hidden sector charged matter multiplets may have sub-ev mass, m hidden = α 4 p M 6 s MP 4 µ α 4 p M 2 W M P, for M s = M W M P 1 11 GeV Paraphotons and para(s)electrons are well motivated Weakly Interacting Sub-eV Particles (WISPs)

24 Light Paraphotons and Minicharged Particles Summary In many realistic extensions of the standard model there are extra hidden sector U(1) gauge bosons, weakly mixing with the photon Hidden sector charged particles get a small electric charge Q h = ǫe = χe h Mixing parameter in many models expected to be in the range χ Its size reflects parameters of the underlying high-energy theory (mass splittings, size of extra dimensions,..) Hidden sector U(1) gauge bosons as well as hidden sector charged particles may be light

25 Light Paraphotons and Minicharged Particles Searches for the effects of kinetic mixing, in particular for paraphotons and mini-charged particles, offer one of the few opportunities to explore the global structure of string compactifications: SM HS [Blumenhagen,Braun,Körs,Lüst 2] Low energy photons shed light on the bulk and the hidden sector