Hidden Secluded Dark Sectors and Heavy Photons€¦ · in dark sector X+ X − 1 2 F Y µ F µ....
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Hidden Secluded Dark Sectors and Heavy Photons Mathew Graham SLAC Summer Institute July 30, 2012
Transcript of Hidden Secluded Dark Sectors and Heavy Photons€¦ · in dark sector X+ X − 1 2 F Y µ F µ....
Hidden Secluded Dark Sectors and Heavy Photons
Mathew GrahamSLAC Summer Institute
July 30, 2012
2012 SLAC Summer Institute Mathew Graham
Where does an extra force fit?
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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 Mathew Graham
Where does an extra force fit?
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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!
DarkForces
2012 SLAC Summer Institute Mathew Graham
Portals to a hidden sector
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Standard Model
SU(3)×SU(2)×U(1)
Dark Sector
??????
“portal”
vector
Higgs
neutrino
axion
�h|h|2|�|2
��(hL)�
1fa
aFµ�F̃µ�ALPSs
dark photon
dark scalar
sterile neutrino
12�FY
µ�F �µ�
2012 SLAC Summer Institute Mathew Graham
Kinetic mixing from the vector portal
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LU(1)� = �14V 2
µ� ��
2Vµ�Fµ� + |Dµ⇥|2 � V (⇥)
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
•extremely general conclusion...even arises from broken symmetries•gives coupling of normal charged matter to the new “dark photon” q=εe
Kinetic Mixingterm
2012 SLAC Summer Institute Mathew Graham
30 decades of heavy photons
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Jaeckel and Ringwald, hep-ph/1002.0329
...there is a lot of physics here!
2012 SLAC Summer Institute 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
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I will try to stick to dark sector, A′, and ε!
2012 SLAC Summer Institute Mathew Graham
What coupling?
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•Coupling is generated from non-perturbative loops •One-loop if the heavy particle is charged under both U(1)s
•Two-loop if one of the U(1)s is embedded into a higher symmetry...
� � egD
16�2...depends on coupling
in dark sector
X+
X−
12�FY
µ�F �µ�
2012 SLAC Summer Institute Mathew Graham
Ok, what about the mass?
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Depending on model, mass scales like: M(A´)/M(W)~ε1-ε1/2
leading toM(A´)~MeV-GeV
α´=αεN. Weiner, JLAB PAC37 Talk
•Could be massless ⇒ millicharges!•Non-perturbative ⇒ chaos!•Same origin as weak scale
⇒ O(MZ)
2012 SLAC Summer Institute Mathew Graham
•FERMI sees it too!
excess in e+/e− ratio
...but not in p/p ratio
Is this astrophysics or particle physics?
A hint from above?
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Unknown source of high energy positrons...
2012 SLAC Summer Institute Mathew Graham
•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
Dark matter annihilation and the dark sector
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2012 SLAC Summer Institute Mathew Graham
Some existing constraints
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gµ-2ge-2
e+e−→µ+µ−γ
couplinglimited
lifetimelimited
2012 SLAC Summer Institute Mathew Graham
Dark photons and the g-2 anomaly
0.01 0.1 110-910-810-710-610-510-410-310-2
0.01 0.1 1
10-910-810-710-610-510-410-310-2
mA' HGeVL
e E137
E141
E774
amae UH3SL
SN
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If the g-2 anomaly is due to a heavy photon
2012 SLAC Summer Institute Mathew Graham
A´ decay products
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...up to ~500 MeV, decay to leptons dominates
2012 SLAC Summer Institute Mathew Graham
A´ Lifetime
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0.01 0.1 110-910-810-710-610-510-410-310-2
0.01 0.1 1
10-910-810-710-610-510-410-310-2
mA' HGeVL
e
amae UH3SL
10 m
1 cm
1 µm
[Rouven Essig]
�c� ��
10�4
�
�2 �100 MeV
mA�
�2
lower ε, lower mass → longer lifetime
Much of parameter space will have displaced vertex
2012 SLAC Summer Institute Mathew Graham
Collider vs. Fixed Target
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Wherever there is a photon there is a dark photon...
Collider Fixed Target
month...much higher backgrounds
2012 SLAC Summer Institute Mathew Graham
Backgrounds at fixed target
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Bethe-HeitlerTwo main
backgrounds
Black: BHRed: Rad.
BH→Ee++Ee−<<EbeamRad→Ee++Ee−~Ebeam
production rates of A’ and radiative are related:
Radiative
Cross-section for BH>>Radiative, but kinematics much different...
Even after energy cut, BH background ~5x radiative
2012 SLAC Summer Institute Mathew Graham
...a little more subtle...
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Problem: cover the low coupling (<10−4), intermediate mass (20-200 MeV) region•low rate ➪ intense beam•high background ➪ high resolution•still high background ➪ measure displaced vertex
Solution: HPS
2012 SLAC Summer Institute Mathew Graham
•high rate, high acceptance, high mass & vertex resolution detector intended to run in Hall B
•Silicon strip tracker inside an evacuated dipole for excellent vtx & mom resolution. Use Si sensors donated from Fermilab & APV25 readout chips•Borrow & reconfigure the CLAS inner calorimeter for high rate triggering
Heavy Photon Search @ Hall
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targetSi tracker
electromagneticcalorimeter
muonsanalyzing magnet
Momentum & Vertex Trigger and Particle ID
2012 SLAC Summer Institute Mathew Graham
The HPS approach
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Δm/m~1%
e+
e��pe+
+ �pe�~10µ
MC •good mass resolution, dominated by MS in the detector•use small beam-spot (~10µm) to constrain A´ to point back to IP
•beat down vertex tails of prompt decays to ~ 0 expected background•tails dominated by fake tracks...rate dependent
•Estimate coverage 10−4>ε>10−5 for 200>mA´>20MeV•running 3 months each at Ebeam=2.2 and 6.6 GeV
2012 SLAC Summer Institute Mathew Graham
HPS Expected Reach
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0.01 0.1 110-1010-910-810-710-610-510-4
0.01 0.1 1
10-1010-910-810-710-610-510-4
mA' HGeVL
a'êa
E137
E141
E774
amae BaBar
α′/α=ε2
Blue: 200nA @ 2.2GeV target: 0.125%
Red: 450nA @ 6.6GeV target: 0.25%
3 months of beam at each energy
solid-2σdashed-5σ
Bump-hunt only
Bump-hunt + Vertex
2012 SLAC Summer Institute Mathew Graham
It’s getting crowded...
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0.01 0.1 1
10-5
10-4
10-3
10-20.01 0.1 1
10-5
10-4
10-3
10-2
mA' HGeVL
e
E137
E141
E774
amae
BaBar
DarkLightAPEX
HPS
HPS
APEX
Test
Mainz
Many experiments in the works to look for Dark Forces:
Mainz and APEX (JLab) ~ forward spectrometersHPS (JLab) ~ compact Si-based vertex-trackerDarkLight (JLab FEL) ~ high acceptance, H2 gas targetHIPS(DESY)~ beam dump (not shown)
2012 SLAC Summer Institute 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
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⇒ many public results already with more on the way...very active area of study!
2012 SLAC Summer Institute Mathew Graham
What now? My conclusions
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• 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!
• Dark matter naturally fits in this dark sector• by the way, this doesn’t override SUSY...dark sector models and SUSY
get along fine!
• 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
2012 SLAC Summer Institute 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
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“DM could have shown it’s face in many places, and didn’t...but has wiggle-room left.” - Rouven EssigApart 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
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