EEöött--WashWash studies ofstudies ofshortshort--distance gravitydistance gravity

Eric G. AdelbergerEric G. AdelbergerUniversity of Washington University of Washington

FacultyFaculty Current Grad studentsCurrent Grad studentsEEGGAA Ted CookTed CookJensJens GundlachGundlach Charlie Charlie HagedornHagedornBlayne Blayne HeckelHeckel Matt TurnerMatt Turner

Will Will TerranoTerranoStaffStaff Todd WagnerTodd Wagner

Erik SwansonErik Swanson

PostdocsPostdocsFrank FleischerFrank Fleischer 1/r1/r22

Seth Seth HoedlHoedl EPEPStephan SchlammingerStephan Schlamminger spinspinKrishna Krishna VenkateswaraVenkateswara

Primary support from NSF Grant PHY0653863 with supplements from Primary support from NSF Grant PHY0653863 with supplements from the DOE Office of Science and to a lesser extent NASAthe DOE Office of Science and to a lesser extent NASA

the Ethe Eöött--WashWash®® group in group in experimental gravitationexperimental gravitation

95% confidence limits as of 200095% confidence limits as of 2000

4 good reasons for studying 4 good reasons for studying shortshort--distance distance ““gravitygravity””

untested regimeuntested regimeprior to 2007 total ignorance for prior to 2007 total ignorance for ll < 100 < 100 µµm m

probe probe spacetimespacetime geometry: extra dimensions geometry: extra dimensions ll=R*=R*

probe the darkprobe the dark--energy length scale with energy length scale with ll = ( = ( ħħcc//ρρDE DE ))1/4 1/4

ρρDE DE =3.8 keV/cm=3.8 keV/cm3 3 corresponds to corresponds to ll = 85 = 85 µµmm

new particles: Yukawa exchange force with new particles: Yukawa exchange force with ll = = ħħ/(mc)/(mc)ll = 50 = 50 µµm corresponds to mcm corresponds to mc22=4 =4 meVmeVstring theorystring theory’’s nominally s nominally masslessmassless ““gravitationallygravitationally””coupled scalar particles (coupled scalar particles (dilatondilaton, , radionsradions, , modulimoduli)? )? chameleons, chameleons, ““fat gravitonsfat gravitons””??

““braneworldbraneworld”” motivationmotivationfor testing the Newtonianfor testing the NewtonianInverse square law Inverse square law

illustration from Savas Dimopoulos

GaussGauss’’s Law and extra dimensionss Law and extra dimensions

the 42the 42--hole inversehole inverse--square law pendulumsquare law pendulum

PhD project of Dan Kapner, PRL 98, 021101(2007)

Mary Levin photo

rotating attractor and its electrostatic shieldrotating attractor and its electrostatic shield

• tightly stretched, 10- μm thick, Au-coated BeCu foil shields electrostatic effects.

• placed 12 μm above rotating attractor

power spectral density of the twist signalpower spectral density of the twist signal

d = detector/foil separation

problems not addressed by our designsproblems not addressed by our designs

alignmentalignmenttemperature effectstemperature effectsdustdustelectrostatic noiseelectrostatic noise

measuring the detectormeasuring the detector--membrane separationmembrane separation

Cmin

making the attractor parallel to the detectormaking the attractor parallel to the detector

gravitational centering of the detector on the gravitational centering of the detector on the attractorattractor

x0 = -0.015±0.007 mm y0 = +0.004±0.002 mm

Dan Kapner assembling his 42-hole instrument

One piece of dust can prevent you from getting to small separations

signal processingsignal processing

these data were taken with thecalibration turn-table stationary

≈≈7x thermal7x thermalamplitudeamplitude

data from 42data from 42--hole Experiment Ihole Experiment I

21ω

42ω

data from 42data from 42--hole Experiment IIhole Experiment II

after we reducedthe lowerattractor diskthickness by140 microns andstraightened the 3.5 micron curvature of the detector ring

21ω

42ω

data from 42data from 42--hole experiment IIIhole experiment III

after replacingthe gold coatingson the detectorand membrane.In the processwe inadvertantlyincreased the detector bend to3.9 microns

21ω

42ω

data fitting procedure

Scanning tunneling microscope study of our molybdenum surfaces

Surface roughness correction increased hole radii and decreased hole thicknesses by 2.2 µm and 2.3 µm, respectively

95% confidence upper limits on ISL 95% confidence upper limits on ISL violationviolation

implications implications our tests have shown that the ISL holds down to 56 our tests have shown that the ISL holds down to 56 mmm m (|(|aa||§§1) with 95% confidence1) with 95% confidence

largest extra dimension must have R* largest extra dimension must have R* §§ 44 44 mmm m

ADD 2ADD 2--equal large extra dimension scenario needs M*equal large extra dimension scenario needs M*¥¥ 3.4 3.4 TeV/cTeV/c2 :2 : ISLISL--violation from violation from radionradion exchange strongly exchange strongly constrains any number of extra dimensionsconstrains any number of extra dimensions

provide strong constraints on couplings of proposed light provide strong constraints on couplings of proposed light scalar or vector bosons including chameleonsscalar or vector bosons including chameleons

possible anomalies seen at shortest length scalespossible anomalies seen at shortest length scales

dilatondilaton must have mass mcmust have mass mc22 rr 3.5 3.5 meVmeV

2 new, very different experiments are now taking data2 new, very different experiments are now taking data

some some ““geegee--whizwhiz”” numbersnumberstypical error corresponds to light spot on detector moving typical error corresponds to light spot on detector moving by 0.6 nmby 0.6 nm

typical torque in our 42typical torque in our 42--hole experiments is hole experiments is ~ 1fN~ 1fN--m with m with statistical uncertainty of ~0.006 statistical uncertainty of ~0.006 fNfN--mm

corresponds to a force ~(40corresponds to a force ~(40±±0.24) 0.24) fNfN

suppose you could cut a postage stamp into 10suppose you could cut a postage stamp into 101212 equal equal piecespieces

typical force is 60 times the weight of 1 of those piecestypical force is 60 times the weight of 1 of those pieces

typical statistical error is ~1/3 the weight of 1 piecetypical statistical error is ~1/3 the weight of 1 piece

Ted Cook’s Fourier-Bessel pendulum

50 50 µµm W detector & attractor with 120m W detector & attractor with 120--fold fold azimuthalazimuthal symmetrysymmetry

mapping the 3mapping the 3--D D geometry of the geometry of the FourierFourier--Bessel Bessel pendulum pendulum

W foils are glued ontoW foils are glued onto3 mm thick glass disks3 mm thick glass disks

Charlie Hagedorn’s parallel plate experimentattractor:“infinite” plane, homogenous gravity field

schematic top view:

No change in torque on pendulum when infinite plane moves back and forth and if 1/r² holds.torsion

pendulum

Charlie Hagedorn’s “infinite”-plate experiment

top view of actual implementation

stretched Ti foil 4 mm

torsion pendulum

Ti, ρ= 4.6 g/cm ³

Ta, ρ= 16.6 g/cm ³

Thin Pt attractor sheet, backing made from Ti:a rim makes the finite attractor look “infinite”: homogenous gravity field

10 holes26 holes

42 holes 120 spokes

conclusionsconclusionsto probe the true geometry of the universe must study to probe the true geometry of the universe must study gravitygravity

this is done most directly by testing the ISLthis is done most directly by testing the ISL

ISL experiments not yet limited by experimental sensitivity, ISL experiments not yet limited by experimental sensitivity, but by but by ““dirtdirt”” effectseffects

ISL experiments already probe interesting regimes that test ISL experiments already probe interesting regimes that test many current speculationsmany current speculations

theorists keep dreaming up possible new phenomenatheorists keep dreaming up possible new phenomena

testing these ideas provides a demanding challenge for testing these ideas provides a demanding challenge for experimentalistsexperimentalists

some referencessome references

details of our inversedetails of our inverse--square law testssquare law testsCD Hoyle et al., PRD 70, 042004 (2004)CD Hoyle et al., PRD 70, 042004 (2004)D.J. D.J. KapnerKapner et al., PRL 98, 021101(2007)et al., PRL 98, 021101(2007)E.G. E.G. AdelbergerAdelberger et al., PRL 98, 131104(2007)et al., PRL 98, 131104(2007)

outdated theoretical and experimental reviewoutdated theoretical and experimental reviewE.G. E.G. AdelbergerAdelberger, B.R. , B.R. HeckelHeckel and A.E. Nelsonand A.E. NelsonAnn. Rev. Ann. Rev. NuclNucl. and Part. Sci. 53, 77 (2003) . and Part. Sci. 53, 77 (2003)

recent general review recent general review ““TorsionTorsion--balance experiments: a lowbalance experiments: a low--energy frontier of energy frontier of particle physicsparticle physics””EGA, J.H. EGA, J.H. GundlachGundlach, B.R. , B.R. HeckelHeckel, S. , S. HoedlHoedl, , and S. and S. SchlammingerSchlamminger, PPNP 62, 102 (2009), PPNP 62, 102 (2009)

some 2some 2σσ implications of our dataimplications of our datainverseinverse--square law holds down to 56 micronssquare law holds down to 56 microns

largest possible size of an extra dimension is largest possible size of an extra dimension is R =R =ll((aa=8/3) = 44 microns=8/3) = 44 microns

for ADDfor ADD’’s 2 equal extra dimensions scenario s 2 equal extra dimensions scenario M*M*rr 3.4 TeV/3.4 TeV/cc22

radion exchange with n extra dimensions gives a radion exchange with n extra dimensions gives a Yukawa force with Yukawa force with aa=n/(n+2) and =n/(n+2) and ll≈≈2.4 mm [ 1 TeV/M*c2.4 mm [ 1 TeV/M*c22]; this implies M*(n=6) ]; this implies M*(n=6) ≈≈ 6.4 6.4 TeV/cTeV/c22

dilaton must have mass mdilaton must have mass mcc22 rr 3.5 meV3.5 meV

Observed dependence Observed dependence of twistof twist--noise on the noise on the separation betweenseparation betweenpendulum and shieldpendulum and shield

Can this be reduced byCan this be reduced byoperating at operating at atat 4 K? 4 K? IonIon--trap cavity QED worktrap cavity QED workhints that this may help hints that this may help

Electrostatic noise is a limiting factorElectrostatic noise is a limiting factor

patchpatch--field effects on the free periodfield effects on the free period

similar effects are seen on the equilibrium anglesimilar effects are seen on the equilibrium angle

the chameleon mechanismthe chameleon mechanismcan circumvent experimental evidence against string theory’s gravitationally coupled low-mass scalars by adding a self-interaction term to the effective potential density

in presence of matter, massless chameleons acquire an effective mass

so that an object’s external field comes only from a thin skin of material of thickness ~ 1/meff (º 60μm)

natural values of b & g are 1

22σσ chameleon constraints chameleon constraints PRL 98, 13104 (2007)PRL 98, 13104 (2007)

natural value

EXCLUDED

Constraints on exotic scalar or vector bosonsConstraints on exotic scalar or vector bosons

SundrumSundrum’’s s ““fat gravitonfat graviton”” forceforce

We published MoWe published Mo--Mo constraints: Mo constraints: now obtaining similar qualitynow obtaining similar qualityWW--W constraints where the W constraints where the ψψpole is in a different placepole is in a different place

Our upper limit is aboutOur upper limit is about10101111 times below PVLAS1.times below PVLAS1.The only way I know to avoidThe only way I know to avoidthis constraint is to invoke this constraint is to invoke chameleons chameleons

the Irvine experimentthe Irvine experiment

Hoskins et al. PRD 32, 3084 (1985)

unifying gravity with the other forces in physics unifying gravity with the other forces in physics is the central problem in fundamental scienceis the central problem in fundamental science

string or M theory provides the only known frameworkstring or M theory provides the only known frameworkfor doing thisfor doing this

BUT: it inherently contains features that have to be BUT: it inherently contains features that have to be hidden from experiment:hidden from experiment:

10 or 11 dimensions10 or 11 dimensions100s of massless scalar particles with 100s of massless scalar particles with ““gravitationalgravitational””

couplingscouplings

must find a way to account for the extreme weaknessmust find a way to account for the extreme weaknessof gravity and the observed of gravity and the observed ““dark energydark energy””

some of these new features could show up in inversesome of these new features could show up in inverse--square law testssquare law tests

Does dark energy define a new Does dark energy define a new fundamental length scale in physics?fundamental length scale in physics?

a second “Planck length”?