Jul 30, 2012 ... How could additional forces have escaped detection? • very high ... fa. aFµν. ˜. F.
µν. ALPSs dark photon dark scalar sterile neutrino. 1. 2. ∈F. Y.
Hidden Secluded Dark Sectors and Heavy Photons Mathew Graham SLAC Summer Institute July 30, 2012
Where does an extra force fit?
http://www.particleadventure.org/inter_summary.html
How could additional forces have escaped detection? • very high mass force carrier • small coupling to SM particles
2012 SLAC Summer Institute
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Mathew Graham
Where does an extra force fit? Dark Forces
http://www.particleadventure.org/inter_summary.html
How could additional forces have escaped detection? • very high mass force carrier • small coupling to SM particles •0 (direct) coupling to SM! 2012 SLAC Summer Institute
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Mathew Graham
Portals to a hidden sector Standard Model
“portal”
Dark Sector ??????
SU(3)×SU(2)×U(1)
vector Higgs neutrino axion 2012 SLAC Summer Institute
1 Y Fµ F 2 2
h |h|
µ
dark photon 2
| |
(hL)
1 µ ˜ aFµ F fa 4
dark scalar sterile neutrino ALPSs Mathew Graham
Kinetic mixing from the vector portal an old idea: if there is an additional U(1) symmetry in nature, there will be mixing between the photon and the new gauge boson Holdom, Phys. Lett B166, 1986
LU (1) =
1 2 Vµ 4
2
Vµ F
µ
+ |Dµ ⇥|
2
V (⇥)
Kinetic Mixing term
•extremely general conclusion...even arises from broken symmetries •gives coupling of normal charged matter to the new “dark photon” q=εe 2012 SLAC Summer Institute
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Mathew Graham
30 decades of heavy photons ...there is a lot of physics here!
Jaeckel and Ringwald, hep-ph/1002.0329 2012 SLAC Summer Institute
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Mathew Graham
Terminology break •
The literature is infested with different terms for (basically) the same things... • • •
dark sector=hidden sector=secluded sector dark photon=hidden photon=heavy photon=A′=U-boson ε2=κ2=α′/α
I will try to stick to dark sector, A′, and ε!
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Mathew Graham
1 Y Fµ F 2
What coupling?
µ
•Coupling is generated from non-perturbative loops •One-loop if the heavy particle is charged under both U(1)s
egD 16 2
...depends on coupling in dark sector
•Two-loop if one of the U(1)s is embedded into a higher symmetry...
X+ X−
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Mathew Graham
Ok, what about the mass? •Could be massless ⇒ millicharges! •Non-perturbative ⇒ chaos! •Same origin as weak scale ⇒ O(MZ)
Depending on model, mass scales like: M(A´)/M(W)~ε1-ε1/2 leading to M(A´)~MeV-GeV 2012 SLAC Summer Institute
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N. Weiner, JLAB PAC37 Talk
α´=αε Mathew Graham
A hint from above? excess in e+/e− ratio ...but not in p/p ratio
•FERMI sees it too!
Unknown source of high energy positrons... Is this astrophysics or particle physics? 2012 SLAC Summer Institute
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Mathew Graham
Dark matter annihilation and the dark sector
•new “dark force” with gauge boson ~ GeV while the dark matter
particle (charged under the new force) ~ TeV •decays to lepton pairs (e+e−, µ+µ−) but pp decays are kinematically forbidden
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Mathew Graham
Some existing constraints ge-2
gµ-2
e+e−→µ+µ−γ
lifetime limited coupling limited
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Mathew Graham
Dark photons and the g-2 anomaly If the g-2 anomaly is due to a heavy photon
10-2
0.01 ae
10-3
0.1 am
1 UH3SL
10-2 10-3
E774
10-4
10-4 E141
10-5
10-5
e
E137
10-6
10-6
10-7
10-7
10-8
10-8
10-9
SN
0.01
0.1 mA' HGeVL
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10-9
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Mathew Graham
A´ decay products
...up to ~500 MeV, decay to leptons dominates 2012 SLAC Summer Institute
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Mathew Graham
A´ Lifetime 10-2 10 2
100 MeV mA
lower ε, lower mass → longer lifetime
0.1
ae
2
10-7
10-5 10
10 m
-6
10-7
10-8
10-8
10-9
10-9
0.01
0.1 mA' HGeVL
1
[Rouven Essig]
Much of parameter space will have displaced vertex 2012 SLAC Summer Institute
-3
10-4
1 cm
-6
10-2 10
1 µm
10-5 10
1 UH3SL
am
10-4 e
c
10
4
-3
0.01
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Mathew Graham
Collider vs. Fixed Target Wherever there is a photon there is a dark photon... Collider Fixed Target
mon th 2012 SLAC Summer Institute
...much higher backgrounds 16
Mathew Graham
Backgrounds at fixed target Two main backgrounds
Bethe-Heitler
Radiative
production rates of A’ and radiative are related:
Black: BH Red: Rad. BH→Ee++Ee−Radiative, but kinematics much different... Even after energy cut, BH background ~5x radiative
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Mathew Graham
...a little more subtle... Problem: cover the low coupling (ε>10−5 for 200>mA´>20MeV •running 3 months each at Ebeam=2.2 and 6.6 GeV
Δm/m~1% +
e ~10µ
pe
+
+ pe
2012 SLAC Summer Institute
e
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Mathew Graham
solid-2σ dashed-5σ
-4
10
HPS Expected Reach 0.01
0.1 am
ae
1 BaBar
-5
10
-6
a'êa
-6
10
E774
-7
10
Bump-hunt only
-8
-7
10
-8
10
10 E141
-9
10
-10
10
α′/α=ε2
10
-5
10 10
-4
Bump-hunt + Vertex
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-10
Red: 450nA @ 6.6GeV target: 0.25% 3 months of beam at each energy
10
E137
0.01
-9
Blue: 200nA @ 2.2GeV target: 0.125%
0.1 mA' HGeVL
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Mathew Graham
It’s getting crowded... 10-2
0.01
0.1
1
am
ae
10-2
BaBar
Mainz
10-3
10-3
APEX Test
HPS
DarkLight
e
E774
APEX
10-4
10-4 E141
HPS
10-5
10-5
E137
0.01
0.1 mA' HGeVL
2012 SLAC Summer Institute
Many experiments in the works to look for Dark Forces:
1
22
Mainz and APEX (JLab) ~ forward spectrometers HPS (JLab) ~ compact Sibased vertex-tracker DarkLight (JLab FEL) ~ high acceptance, H2 gas target HIPS(DESY)~ beam dump (not shown)
Mathew Graham
Other direct dark force searches • Searches at e e colliders: BaBar & Belle(II), KLOE, BES + −
• • •
•
Lower luminosity + lower backgrounds Higher mass reach (up to ~10GeV) “exotic” dark force states: dark higgs, dark mesons
Searches at hadrons colliders:
• • •
ATLAS/CMS & CDF/D0
possible unique production path ⇒ cascades from SUSY particles “lepton-jets” signatures along with typical di-lepton mass peak potentially covers vast area of coupling-mass space, but with model assumptions
⇒ many public results already with more on the way...very active area of study! 2012 SLAC Summer Institute
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Mathew Graham
What now? My conclusions • • • •
The search for new gauge bosons has a long history over a huge range of mass scales Something like a dark photon is very well theoretically motivated and if we live in a GU universe it probably exists
•
What coupling? What mass? Who knows? I have my favorite region!
•
by the way, this doesn’t override SUSY...dark sector models and SUSY get along fine!
Dark matter naturally fits in this dark sector It’s very cool to think that there might be very complicated, very different physics going on all around us which we can’t examine but through this weak, tenuous connection
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Mathew Graham
What now next? •
Ok, say we are seeing DM annihilating (maybe via dark photons) in the PAMELA & FERMI data...what else should we see
• •
•
•
f(e+/e−) should cut off at ~ DM mass high energy photons from inverse Compton scattering & final state radiation ⇒ constraints from Fermi are discouraging imprints on the CMB ⇒ PLANK will be crucial...2013?
Possibly large impact on direct DM experiments
• • •
iDM ⇒ lower recoil energy DAMA/CoGeNT/CRESST anomalies? Xenon100, CDMS are putting big dent in iDM parameter space
“DM could have shown it’s face in many places, and didn’t...but has wiggle-room left.” - Rouven Essig Apart from these anomalies, the upcoming direct heavy-photon searches will block out a very interesting part of parameter space...maybe the dark sector will show it’s head before dark matter 2012 SLAC Summer Institute
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Mathew Graham