Amol Upadhye (ANL): How Dark Is Dark Energy?

Chameleon dark energy Chameleon and thin-shell eﬀects GammeV-CHASE Oscillation Introduction

1 Cosmic acceleration is the greatest mystery in cosmology. cosmological constant? scalar field, modified gravity ⇒ w(z) 6= −1, fifth forces, etc. 2 Chameleon dark energy looks like cosmological constant on large scales evades fifth force constraints by becoming massive in high-density environments photon coupling ⇒ oscillation 3 GammeV-CHASE afterglow experiment produce chameleon particles through oscillation trap particles inside chamber “afterglow” as particles oscillate back into photons constraints on chameleon parameter space published

Amol Upadhye How dark is dark energy? nonlinear V 0 linear matter coupling photon coupling ⇒ nonlinear e.o.m. 1 2 2 ∼ βmρφ/MPl ∼ 2 βγφ(B − E )/MPl mass of field depends on matter chameleon- distribution photon effective mass meff higher in denser oscillation in environments background ⇒ chameleon and thin-shell effects magnetic field

Chameleon dark energy Chameleon and thin-shell eﬀects GammeV-CHASE Oscillation Chameleon scalar ﬁeld

Action for a photon-coupled chameleon ﬁeld:

Z βmφ βγ φ 4 h 1 2 1 µν i S = d x − (∂φ) − V (φ) + L (e MPl g ) − e MPl F F 2 mat µν 4 µν

Amol Upadhye How dark is dark energy? mass of field depends on matter chameleon- distribution photon effective mass meff higher in denser oscillation in environments background ⇒ chameleon and thin-shell effects magnetic field

Chameleon dark energy Chameleon and thin-shell eﬀects GammeV-CHASE Oscillation Chameleon scalar ﬁeld

Action for a photon-coupled chameleon ﬁeld:

Z βmφ βγ φ 4 h 1 2 1 µν i S = d x − (∂φ) − V (φ) + L (e MPl g ) − e MPl F F 2 mat µν 4 µν

nonlinear V 0 linear matter coupling photon coupling ⇒ nonlinear e.o.m. 1 2 2 ∼ βmρφ/MPl ∼ 2 βγφ(B − E )/MPl

Amol Upadhye How dark is dark energy? Chameleon dark energy Chameleon and thin-shell eﬀects GammeV-CHASE Oscillation Chameleon scalar ﬁeld

Action for a photon-coupled chameleon ﬁeld:

Z βmφ βγ φ 4 h 1 2 1 µν i S = d x − (∂φ) − V (φ) + L (e MPl g ) − e MPl F F 2 mat µν 4 µν

nonlinear V 0 linear matter coupling photon coupling ⇒ nonlinear e.o.m. 1 2 2 ∼ βmρφ/MPl ∼ 2 βγφ(B − E )/MPl mass of field depends on matter chameleon- distribution photon effective mass meff higher in denser oscillation in environments background ⇒ chameleon and thin-shell effects magnetic field

Amol Upadhye How dark is dark energy? Chameleon dark energy Chameleon and thin-shell eﬀects GammeV-CHASE Oscillation Chameleon and thin-shell eﬀects

1 vacuum

0.8 force on test particle: F ∝ dφ/dx 0.6 bulk φ (x)/ φ 0.4

0.2 thickness 0.3 1 [m 3 eff -1 10 ] 30 0 -20 -15 -10 -5 0 5 10 15 20 -1 x [meff] (AU, Gubser, Khoury 2006) Amol Upadhye How dark is dark energy? Chameleon dark energy Chameleon and thin-shell eﬀects GammeV-CHASE Oscillation Chameleon-photon oscillation

γ ↔ φ conversion in background B~ ﬁeld (from φF 2 interaction) Oscillation probability β2 B2t2 ~ γ massless limit, parallel to B: Pγ↔φ = 2 4MPl (AU, Steﬀen, Weltman 2010) conversion rate for a chameleon particle propagate through B~ measure particle content after time ∆t Pγ↔φ(∆t) conversion rateΓ= ∆t average over particles to get total rate

Amol Upadhye How dark is dark energy? Chameleon dark energy Chameleon and thin-shell eﬀects GammeV-CHASE Oscillation Window as a quantum measurement device

density ρ background φ0 φ0 + δφ photon

0 5 10 15 20 -1 x [meff ]

Amol Upadhye How dark is dark energy? Chameleon dark energy Experimental setup GammeV-CHASE Constraints A simple afterglow experiment

(a) Production phase: photons streamed through B~ 0 region; some oscillate into chameleons

(b) Afterglow phase: chameleons slowly oscillate back into photons, escaping chamber

Amol Upadhye How dark is dark energy? Chameleon dark energy Experimental setup GammeV-CHASE Constraints GammeV-CHASE apparatus

1 Multiple magnetic ﬁeld runs 2 Partitioning of magnetic ﬁeld region 3 Modulation of detector 4 Vacuum maintained by ion pump

Amol Upadhye How dark is dark energy? Chameleon dark energy Experimental setup GammeV-CHASE Constraints Conversion rate in GammeV-CHASE

0.0001

1e-06 decay

1e-08 afterglow

1e-10 rate [Hz]

1e-12 ξ ref 4 1e-14 0 (V∝ φ ) π/3 (V∝ 1/φ) π (V∝ exp φ) 1e-16 0.0001 0.001 0.01 0.1

meff(chamber) [eV] (AU, et. al., 2012 (in prep.)) Amol Upadhye How dark is dark energy? Chameleon dark energy Experimental setup GammeV-CHASE Constraints Expected afterglow signal

1e+12 observation period βγ=3e11 1e+10

] 1e+08 -1

1e+06

10000

afterglow rate [sec 100 5.0 T

1 2.2 T 0.01 -1500 -10001.0 T -500 0 500 1000 1500 2000 2500 3000 0.45 T time [sec]

0.2 T Amol Upadhye How dark is dark energy? Chameleon dark energy Experimental setup GammeV-CHASE Constraints Expected afterglow signal

1e+12 observation period βγ=1e13 1e+10

] 1e+08 -1

5.0 T 1e+06 2.2 T 10000 1.0 T

afterglow rate [sec 100 0.45 T 0.2 T 1 0.09 T 0.05 T 0.01 -1500 -1000 -500 0 500 1000 1500 2000 2500 3000 time [sec]

Amol Upadhye How dark is dark energy? Chameleon dark energy Experimental setup GammeV-CHASE Constraints Expected afterglow signal

1e+12 observation period βγ=3e14 1e+10 5.0 T 2.2 T

] 1e+08 1.0 T -1 0.45 T 0.2 T 1e+06 0.09 T 10000 0.05 T

afterglow rate [sec 100

0.01 -1500 -1000 -500 0 500 1000 1500 2000 2500 3000 time [sec]

Amol Upadhye How dark is dark energy? Chameleon dark energy Experimental setup GammeV-CHASE Constraints Expected afterglow signal

5.0 T 1e+12 2.2 T β =1e16 1.0 T observation period γ 1e+10 0.45 T 0.2 T 0.09 T 0.05 T ] 1e+08 -1

1e+06

10000

afterglow rate [sec 100

0.01 -1500 -1000 -500 0 500 1000 1500 2000 2500 3000 time [sec]

Amol Upadhye How dark is dark energy? Chameleon dark energy Experimental setup GammeV-CHASE Constraints GammeV-CHASE constraints

1e+17 Collider constraints 1e+16 γ

β 1e+15

1e+14 CHASE constraints

1e+13 GammeV 1e+12 constraints photon coupling

1e+11 scalar pseudoscalar 1e+10 1e-05 0.0001 0.001 0.01 0.1

effective mass meff [eV]

(Steﬀen, AU, et. al., 2010) Amol Upadhye How dark is dark energy? Chameleon dark energy Experimental setup GammeV-CHASE Constraints 4 4−N N Constraints on dark energy, V (φ) ≈ MΛ + MΛ φ

1e+17 1e-2 1e+16 Collider constraints ] γ 1e-3 β 1e+15 -1 1e-4

1e+14 [GeV 1e-5 Pl 1e+13 / M γ

N=-1 1e-6 β

1e+12 N=-2 = photon coupling γ N=-4 1e-7 g 1e+11 N=4, λ=10-2 -4 N=4, λ=10 1e-8 1e+10 10000 1e+08 1e+12 1e+16 1e+20 1e+24 β matter coupling m (Steﬀen, AU, et. al., 2010) Amol Upadhye How dark is dark energy? Chameleon dark energy Experimental setup GammeV-CHASE Constraints Conclusions

1 Laboratory searches for dark energy are complementary to cosmological probes. 2 GammeV and GammeV-CHASE attempted to produce, trap, and detect chameleon dark energy through its afterglow. 3 GammeV was a simple modiﬁcation of an axion experiment, suggesting possibilities for future experiments. 4 GammeV-CHASE published constraints in Steﬀen, AU, Baumbaugh, Chou, Mazur, Tomlin, Weltman, Wester 2010.

excluded 4 orders of magnitude in βγ at meﬀ = MΛ bridged gap between GammeV and collider constraints

Amol Upadhye How dark is dark energy? Chameleon dark energy Experimental setup GammeV-CHASE Constraints

The End.

Amol Upadhye How dark is dark energy?