Searching for Dark Forces at colliders. • Fixed-Target Dark Force Searches ... of
dark U(1) to EM-charged particles. ∈eA0JEM. A′. L. 1. 4. F. 2. Y. 1. 4. F02 +.
Searching for Dark Forces at Accelerators Natalia Toro Perimeter Institute CAP Congress 2013
Dark Forces Below the Weak Scale • Theory, motivation, and goals for new-particle searches at the GeV-scale • Searching for Dark Forces at colliders • Fixed-Target Dark Force Searches
Copernican Particle Physics? p+, n, e–
?
?
...
?
?
Copernican Particle Physics? p+, n, e–
? ?
?
... ?
extension of Standard Model? (axion, superpartner, ...)
Is there room for new physics not charged under Standard Model forces?
Completely new physics?
How to look for physics FAR beyond the SM? Accessible mass isn’t enough – need interactions Interactions allowed by all symmetries tend to involve many fields simultaneously ⇒ suppressed by high power of mass-scale at which interactions are generated, e.g.
( ¯e
e )SM ( ¯
)new /⇤
2
Even if ! is light, large " ⇒ unobservable effect. The few operators with no !-suppression represent opportunity to probe new physics that decouples from SM at any " (even near the Planck scale). – Must involve symmetry-invariant combinations of fields with mass-dimension ≤4
4
The “Portals” Neutrino Portal
⌫
Higgs Portal
h
Vector Portal
1 2 Y
(kinetic mixing)
(hL)⇥
sterile neutrinos?
2
2
Y Fµ
0µ
|h| |⇥| F
exotic rare Higgs decays?
[Holdom ’86]
Generic low-energy remnants of any non-SM sector Only light-vector portal is truly accessible in low-energy production (e & p couplings to h, " are small)
5
Vector-Portal Interactions massive ^
Consequences of a new mixed U(1): L
1 2 4 FY
1 02 4F
+
✏Y 2 FY 0 0
“heavy (dark) photon”
F0 2
02
+ eAY JY + gA J + m A
Y Y A ! A Diagonalize: µ µ
✏Y A0µ
A!
0 ✏eA JEM Induces coupling of dark U(1) to EM-charged particles
e (✏ = ✏Y cos ✓W ) mediates production and (if m>2 me)decay
What are reasonable couplings and masses?
e
+
e
µ,⇡, . . . 6
Sources and Sizes of 1 Y 0µ Kinetic Mixing 2 Y Fµ F • If absent from fundamental theory, can still be generated by perturbative (or non-perturbative) quantum effects – Simplest case: one heavy particle $ with both EM charge & dark charge
# γ
e
gD
e gD generates ✏ ⇠ 16⇡ 2 log
A m M⇤
0 ⇠ 10
2
10
4 7
Sources and Sizes of 1 Y 0µ Kinetic Mixing 2 Y Fµ F • If absent from fundamental theory, can still be generated by perturbative (or non-perturbative) quantum effects – In Grand Unified Theory, symmetry forbids treelevel & 1-loop mechanisms. GUT-breaking enters at 2 loops
# γ
e
X
gD
A
3
5
0
10 generating ✏ ⇠ 10 (→ 10 7 if both U(1)’s are in unified groups)
8
Wide Parameter Space: Hidden Vectors Nuclear scale
THIS TALK [Figure from Intensity Frontier report – Javier Redondo]
new particles
Sources and Sizes of Mass Term • MeV-to-GeV is allowed at couplings >10-7 • Possible origin: related to MZ by small parameter – e.g. supersymmetry+kinetic mixing ⇒ scalar coupling to SM Higgs, giving
mA 0
p ⇠ ✏ MZ . 1GeV
[e.g. Cheung, Ruderman, Wang,Yavin; Katz, Sundrum; Morrissey, Poland, Zurek]
• motivated by g-2 and dark matter anomalies a motivated target of opportunity
10
Target of Interest? Precision Anomalies Muon g-2 U(1)D coupling modifies (g-2)$, with correct sign. %~1-3 10–3 can explain discrepancy with Standard Model
Muonic hydrogen MeV-scale force carriers can explain the discrepancy between ($-,p) Lamb shift [Pohl et al. 2010] and other measurements of proton charge radius. Requires couplings beyond kinetic mixing (lepton flavor-violating component) [Tucker-Smith & Yavin, 1011.4922]
Target of Interest? Dark Matter Interactions High-energy cosmic e+/e– (PAMELA, FERMI, AMS) Thermal DM charged under U(1)D can have large local annihilation rate (Sommerfeld enhancement) and hard, lepton-rich decays [Arkani-Hamed, Finkbeiner, Slatyer, Weiner; Cholis, Finkbeiner, Goodenough, Weiner; Pospelov & Ritz]
No signals in other probes of DM annihilation – constrained but not excluded – interesting ways out of constraints
[Finkbeiner et al, 1011.3082]
Light dark matter hints (DAMA, CoGeNT, CRESST, CDMS-Si) Many instrumental challenges & constraints… A dark force easily reconciles ≲10 GeV DM with Standard-Model-like decays of Z and h
[CDMS 1304.4279]
Searching For MeV-GeV Dark Forces: Production 1 2 Y
Y Fµ
F
0µ
0
→ ✏eA JEM ⇒ Particles of EM charge q
get effective U(1)’ charge ϵq
Production n n A
: n o i t a ihil +
e
A&
e d a R
: n o i t ia e
A&
h t g i h o s n e r ty – i u q e R inosi gy! r m e u l h en hig 13
Broad Array of Searches! (done, ongoing, planned)
High Energy Hadron Colliders (indirect) – New heavy particles can decay into dark sector “lepton jets” (ATLAS, CMS, CDF & D0)
Colliding e+e-: On- or Off- shell A’, X=dark sector or leptons & pions (BaBar, BELLE, BES-III, CLEO, KLOE) tomorrow:
E1
A
E1 x
E1 (1
x)
“Fundamental Symmetries 4” Fixed-Target: Electron or Proton collisions, A’ decays to di-lepton, pions, invisible (FNAL, JLAB (Hall A & B & FEL), MAMI (Mainz), WASA@COSY ...)
14
Searching For MeV-GeV Dark Forces: Decay “Minimal” Decay: +
e
A& e (also !+!–, %+%–, …)
via same mixing operator as production ⇒ tiny width 2
⇠ ✏ ↵mA0 15
Searching For MeV-GeV Dark Forces: Decay “Minimal” Decay:
“Generic” Decay:
+
e
A&
A& e
(also !+!–, %+%–, …)
via same mixing operator as production ⇒ tiny width 2
⇠ ✏ ↵mA0
(not "-supressed!) If any dark-sector matter # has ¯ m#2 charged particles
Important! Testing the idea of dark sectors requires a collection of searches sensitive to all possible A& decays, visible & invisible. 15
Wide Breadth of Searches (just a few representative examples) Minimal Decay Non-Abelian Dark Sector KLOE, 1110.0411
0908.2821
! ⌘AD ! ⌘(e+ e )
Reach: 0 ↵ /↵ ⇠ 10
5
Vector + Higgs:
BF UL 90% C.L. (10 -6)
Invisible Decay BABAR
[KLOE 1107.2531] [BaBar 1202.1313]
Stat errors only Stat ⊕ Syst errors
Preliminary
[hep-ex/0808.0017]
10
1
0
1
2
3
4
5
6
7 8 m 0 (GeV)
16
Advantages of Flavor Factories • Highest collider (Lumi.)/(ECM)2 in the world • 4% detectors & clean reconstruction – Broadest possible search program: A&→l+l–, invisible A&, multi-body cascade decays
• Large dataset “in the bank” with dramatic improvements possible from future SuperB – Many searches viable using standard triggers – Some decays (e.g. '+invisible A&) require and motivate new, non-standard trigger
Fixed-Target Advantages Fixed-Target
LUMINOSITY
e+e-
~1023
1011 e-
1011 e-
atoms in target N(hard scatter) ~ 0.01 – 1 per electron 1
O(few) ab
CROSS-SECTION – Scales as Aʹ′ mass, not beam energy – Coherent scattering from nucleus
A
E1
per day
1011 e+
N(hard scatter) ~ 1 per crossing
O(few) ab
1
per decade
E1 x E1 (1
x) µ+
Nucleus
µ 3
⇤
2 2
2 2
Z ⇥ m2
O(10 pb)
⇤
⇥
E2
O(10 f b)
Fixed-Target Territory: 0.001 10-4
“Minimal” visible decay 0.01
0.1
1
(l+l–)
10-4
a m, 5 s
10-5
10-5
one-loop
KLOE
a m,±2 s favored
-6
E774
BaBar APEXêMAMI Test Runs
ae
-7
10-6 -7
10
10
a'êa
0
↵ /↵
10
E141
10-8
two-loop (GUT)
10-8 Orsay
10-9
direct decay
10-10
10-9 10-10
U70
10-11 0.001
0.01
0.1 mA' HGeVL
mA0 (GeV)
1
threeloop
10-11
19
Fixed-Target Territory: 0.001 10-4
“Minimal” visible decay 0.01
0.1
1
(l+l–)
10-4
a m, 5 s
10-5
10-5
one-loop
KLOE
a m,±2 s favored
-6
E774
10-7
a'êa
0
↵ /↵
10
10-6
BaBar APEXêMAMI Test Runs
ae
two-loop ⇥c⇤ ⇡ 1 mm (⇥/10) 10 -7 10 (GUT)
km
10-9 10-10
U70
10-11 0.001
0.01
0.1 mA' HGeVL
mA0 (GeV)
1
threeloop
10-11
19
Beam-Dump Limits 0.001 10-4
0.01
shield 1 10-4 (10 cm - 100 m)
0.1
a m, 5 s
e beam
10-5
decay volume (50 cm - 100 m)
10-5
KLOE
a m,±2 s favored
-6
E774
10-7
BaBar APEXêMAMI Test Runs
10-6
thick target
ae
tracking, calorimetry, ...
Decay in shield
a'êa
0
↵ /↵
10
10-7
E141
10-8 Orsay
10-9 10-10
direct decay
Rate too small and/ or decay too far
10-8 10-9 10-10
U70
10-11 0.001
0.01
0.1 mA' HGeVL
mA0 (GeV)
1
10-11
20
Electron Beam Sensitivity Experiments under development in next few years will explore most parameter space below 300 MeV 0.001 10-4 10-5
VEPP3
a'êa0 ↵ /↵
0.1
1
a m, 5 s
BaBar
E774 DarkLight
10
10-11 0.001
direct decay
10-6
10-9
HPS
Orsay
10
Newport News VA
10-8
E141
-9
10
JLAB CEBAF
10-7
APEX
HPS
10-8 -10
APEXêMAMI Test Runs
ae
-4
10-5
KLOE
a m,±2 s favored
10-6 10-7
0.01
MAMI/A1
(sensitivity not shown) Mainz Microtron MAMI-C: Emax=1.6 GeV Mainz, Germany [1101.4091]
A1 Experiment -10
10
U70
0.01 0.1 mA' HGeVL
1
APEX, HPS, Mainz strategies following scenarios discussed in Phys.Rev. D80 (2009) 075018 (Bjorken, Essig, Schuster, NT)
10-11
Cascade of 3 race track microtrons + Harmonic Double Sided Microtron (HDSM)
HIGH Intensity HIGH Resolution HIGH Polarization HIGH Reliability
MAMI C beam parameters: • 1604 MeV, 'E2 charged particles
30
What if the dark photon doesn’t come back? Collider: look for photon recoiling off invisible A& resonance Fixed-target: A& is produced, then decays to invisible ' (dark matter?):
+
Look for neutral current scattering of '
31
proton & electron Beams Proton beams: – Use existing accelerator " detectors – Large "-scattering backgrounds, almost irreducible Electron beams: – Need new detector behind dump (but forward production ⇒ can be small)
– Minimal beam-related backgrounds but using CW e– beam ⇒ limited by cosmogenic bkg
relative merits & complementarity of different scattering signals not thoroughly explored in either case 32
Prospects mA’=2 m'
mA’
B-factories %2≳10–5:6 e–
beam %2≳10–6:7 m(–(→)A’ 10–7:9
no A& → !! decay (still interesting as a DM search)
increasing mass coverage but decreasing coupling sensitivity
m' 33
Status and Prospects 10-4 -5
10
(g-2)!
oneloop
(g-2)! ± 2" fit
BaBar
K + Æ p+ + inv.
10-7
[arXiv:1307.6554 Izaguirre, Krnjaic, Schuster, NT]
(GUT)
10-8 10-9
m c = 68 MeV, a D = 0.1 0.1 m A' HGeVL
Harder than visible A! searches! – signal ∝ )4 not )2
But important parameter two-loop range
e2
10-6
Hg- 2Le
1
– (g-2)! preferred region – motivated )2 range – generic possibility of light dark-sector matter – ! dark matter not constrained by direct detection or LHC
Red lines = quasi-elastic scattering behind JLab-like beam dump, with (top to bottom) no neutron bg rejection, 1/20 rejection, 10-3 rejection Dedicated MiniBoone run sensitivity comparable to middle line [arXiv: 1211.2258]; see also [arXiv:1309.5084 Essig et al] for impact of aggressive analysis with new triggers at Belle 2
34
Status and Prospects 10-4 -5
10
Hg- 2Le
(g-2)!
± 2" fit
BaBar
K + Æ p+ + inv.
10-7 -8
10
10-9
[arXiv:1307.6554 Izaguirre, Krnjaic, Schuster, NT]
(GUT)
LSND
[1205.3499 deNiverville, McKeen,Ritz]
m c = 10 MeV, a D = 0.1 0.1 m A' HGeVL
– signal ∝ )4 not )2
But important parameter two-loop range
e2
10-6
oneloop
(g-2)!
Harder than visible A! searches!
1
– (g-2)! preferred region – motivated )2 range – generic possibility of light dark-sector matter – ! dark matter not constrained by direct detection or LHC
Red lines = quasi-elastic scattering behind JLab-like beam dump, with (top to bottom) no neutron bg rejection, 1/20 rejection, 10-3 rejection Dedicated MiniBoone run sensitivity comparable to middle line [arXiv: 1211.2258]; see also [arXiv:1309.5084 Essig et al] for impact of aggressive analysis with new triggers at Belle 2
34
Conclusions • Dark Forces are an exciting window into physics far beyond the Standard Model – Possible connections to dark matter and physics at very high scales
• Several mass ranges are testable in moderatescale experiments – New-particle searches in B-factories – many results already, continuing to extend – Dedicated fixed-target experiments are extending range to much lower couplings – Many recent developments in searches for invisible A& decays
• A lot of uncharted territory: opportunities for further exploration – and maybe discovery – abound!
Conclusions 0.001 10-4 • 10
VEPP3
↵ /↵
a'êa0
10-8
m, 5 s
KLOE
favored –a Possible connections to dark matter and physics at -6 BaBar 10 E774 very high scales 10-6 K Æ p + inv. a m,±2 s
10-6 10-7
Hg- 2Le
0.01 Forces 0.1 1 an-4exciting window into Dark are 10 a physics far beyond Standard Model -5 -5the 10 10 APEXêMAMI Test Runs
e
+
10-7
+
e2
-5
10-4
• Several mass ranges are -7testable in moderate-8 10 E141 10 scale experiments
DarkLight
-9
HPS
LSND 10-9 in B-factories – New-particle searches – many results -8 10 already, continuing to extend 10-10 m c = 10 MeV, a D = 0.1 U70 – Dedicated fixed-target are extending -9 -11 experiments 10 10 0.1 1 0.01 range 0.1 to much1lower couplings m A HGeVL mA' HGeVL – Many recent developments in searches for invisible A& decays
Orsay
10
10-10 10-11 0.001
APEX
HPS
'
• A lot of uncharted territory: opportunities for further exploration – and maybe discovery – abound!
