Presentation on theme: "New limits on spin-dependent Lorentz- and CPT-violating interactions Michael Romalis Princeton University."— Presentation transcript:
1New limits on spin-dependent Lorentz- and CPT-violating interactions Michael Romalis Princeton University
2Experimentalist’s Motivation Is the space truly isotropic?Remove magnetic field, other known spin interactionsRemove the EarthDESpin UpSpin DownIs there still an “Up” and a “Down” ?First experimentally addressed by Hughes, Drever (1960)V.W. Hughes et al, PRL 4, 342 (1960)R. W. P. Drever, Phil. Mag 5, 409 (1960); 6, 683(1961)
3Is the space really isotropic? –ask astrophysicists Cosmic Microwave Background Radiation MapThe universe appears warmer on one side!v = 369 km/sec ~ 10-3 cWell, we are actually moving relative to CMB rest frameSpace and time vector components mix by Lorentz transformationA test of spatial isotropy becomes a true test of Lorentz invariance (i.e. equivalence of space and time)
4A theoretical framework for Lorentz violation Introduce an effective field theory with explicit Lorentz violationam,bm,cmn,dmn are vector fields in space with non-zero expectation valueVector and tensor analogues to the scalar Higgs vacuum expectation valueSurprising bonus: incorporates CPT violation effects within field theoryGreenberg: Cannot have CPT violation without Lorentz violation (PRL 89, (2002)CPT-violating interactions break Lorentz symmetry, give anisotropy signalsCan search for CPT violation without the use of anti-particlesL=–y(m+agb5)i2ncmnda,b - CPT-oddc,d - CPT-evenFermions:Alan KosteleckyAlthough see arXiv: v1
5Phenomenology of Lorentz/CPT violation Modified dispersion relations: E2 = m2 + p2 + h p JacobsonAmelino-Camelinm - preferred direction, h ~ 1/MplApplied to fermions: H = h m2/MPl S·nNon-commutativity of space-time: [xm,xn] = qmn Witten, Schwartzqmn - a tensor field in space, [q] = 1/E2Interaction inside nucleus: NqmnsmnN eijkqjkSi Pospelov,Carrollyhg=m25)(nLEffective Lagrangian:Myers, Pospelov, SudarskySpin coupling to preferred direction))((abmnq=FL
6Summary of SERF Atomic Magnetometer Alkali metal vapor in a glass cellLinearly PolarizedProbe lightMagnetizationMagnetizationMagnetic FieldCircularly PolarizedPumping lightCell contents[K] ~ cm-3He buffer gas, N2 quenchingWith optically pumped alkali atom vapor, we can make a sensitive magnetic field sensor without cryogenic maintenance.Alkali atoms will be polarized by absorbing circularly polarized light due to the selection rule.And this makes total magnetization.The magnetization will be tipped around the magnetic field. In this case, the By field going through the screen.The tipping makes x component of magnetization, this gives the different refraction indexes for the right and the left circularly polarized lights, respectively.As a result, the cell rotates the polarization angle of the linearly polarized probe light.So we can measure the By field by detecting this angle rotation.zPolarization angle rotation Byxy
7Turn most-sensitive atomic magnetometer into a co-magnetometer! K-3He Co-magnetometerOptically pump potassium atoms at high density ( /cm3)2. 3He nuclear spins are polarized by spin-exchange collisions with K vapor3. Polarized 3He creates a magnetic field felt by K atoms4. Apply external magnetic field Bz to cancel field BKK magnetometer operates near zero magnetic field5. At zero field and high alkali density K-K spin-exchange relaxation is suppressed6. Obtain high sensitivity of K to magnetic fields in spin-exchange relaxation free (SERF) regimeTurn most-sensitive atomic magnetometer into a co-magnetometer!BK=8p3kMHeJ. C. Allred, R. N. Lyman, T. W. Kornack, and MVR, PRL 89, (2002)I. K. Kominis, T. W. Kornack, J. C. Allred and MVR, Nature 422, 596 (2003)T.W. Kornack and MVR, PRL 89, (2002)T. W. Kornack, R. K. Ghosh and MVR, PRL 95, (2005)
9Magnetic field sensitivity Best operating regionSensitivity of ~1 fT/Hz1/2 for both electron and nuclear interactionsFrequency uncertainty of 20 pHz/month1/2 for 3He20 nHz/month1/2 for electronsReverse co-magnetometer orientation every 20 sec to operate in the region of best sensitivity
10Have we found Lorentz violation? Rotating K-3He co-magnetometerRotate – stop – measure – rotateFast transient response crucialRecord signal as a function of magnetometer orientationHave we found Lorentz violation?
11Long-term operation of the experiment N-S signal riding on top of Earth rotation signal,Sensitive to calibrationE-W signal is nominally zeroSensitive to alignmentFit to sine and cosine waves at the sidereal frequencyTwo independent determinations of b components in the equatorial plane20 days of non-stop running with minimal intervention
12Final results Previous limit |bnxy| = (6.4 ± 5.4) 10-32 GeV Anamolous magnetic field constrained:bxHe-bxe = fT ± fTstat ± fTsysbyHe-bye = fT ± fTstat ± fTsysSystematic error determined from scatter under various fitting and data selection proceduresFrequency resolution is 0.7 nHzAnamalous electron couplings be are constrained at the level of fT by torsion pendulum experiments (B.R. Heckel et al, PRD 78, (2008).)3He nuclear spin mostly comes from the neutron (87%) and some from proton (-5%) Friar et al, Phys. Rev. C 42, 2310 (1990) and V. Flambaum et al, Phys. Rev. D 80, (2009).bxn = (0.1 ± 1.6)10-33 GeVbyn = (2.5 ± 1.6)10-33 GeV|bnxy| < 3.7 10-33 GeV at 68% CLJ. M. Brown, S. J. Smullin,T. W. Kornack, and M. V. R., Phys. Rev. Lett. 105, (2010)Previous limit|bnxy| = (6.4 ± 5.4) 10-32 GeVD. Bear et al, PRL 85, 5038 (2000)
14Recent compilation of CPT limits Many new limits in last 10 years10-33 GeVplMmb2~hm - fermion mass or SUSY breaking scaleExisting limits: h ~1/Mpl effects are quite excludedNatural size for CPT violation ?Need 10-37GeV for 1/Mpl2 effectsV.A. Kostelecky and N. RussellarXiv: v3
15CPT-even Lorentz violation =–y(m+agb5)i2ncmnda,b - CPT-oddc,d - CPT-evenMaximum attainable particle velocityImplications for ultra-high energy cosmic rays, Cherenkov radiation, etcBest limit c00 ~ from Auger ultra-high energy cosmic raysMany laboratory limits (optical cavities, cold atoms, etc)Motivation for Lorentz violation (without breaking CPT)Doubly-special relativityHorava-Lifshitz gravityColeman and GlashowJacobson)ˆ1(00kjjkMAXvc-=Something special needs to happen when particle momentum reaches Plank scale!
16Search for CPT-even Lorentz violation with nuclear spin Need nuclei with orbital angular momentum and total spin >1/2Quadrupole energy shift proportional to the kinetic energy of the valence nucleonPreviosly has been searched for in two experiments using 201Hg and 21Ne with sensitivity of about 0.5 mHzBounds on neutron cn~10-27 – already most stringent bound on c coefficient!Suppressed by vEarth
17First results with Ne-Rb-K co-magnetometer Replace 3He with 21NeA factor of 10 smaller gyromagnetic ratio of 21Ne makes the co-magnetometer have 10 times better energy resolution for anomalous interactionsUse hybrid optical pumping KRb21NeAllows control of optical density for pump beam, operation with 1015/cm3 Rb density, lower 21Ne pressure.Eventually expect a factor of 100 gain in sensitivityDifferences in physics:Larger electron spin magnetization (higher density and larger k0)Faster electric quadrupole spin relaxation of 21NeQuadrupole energy shifts due to coherent wall interactionsFast damping of transientsSensitivity already better than K-3He
18N-S E-W 21Ne Semi-sidereal Fits A< 1 fT Data not perfect, but already an order of magnitude more sensitive than previous experimentsN-SA< 1 fTE-W
19Systematic errorsMost systematic errors are due to two preferred directions in the lab: gravity vector and Earth rotation vectorIf the two vectors are aligned, rotation about that axis will eliminate most systematic errorsAmundsen-Scott South Pole StationWithin 100 meters of geographic South PoleNo need for sidereal fitting, direct measurement of Lorentz violation on 20 second time scale!
20Classic axion-mediated forces Monopole-Monopole:Monopole-Dipole:Dipole-Dipole:J. E. Moody and F. Wilczek, Phys. Rev. D 30, 130 (1984)
21Search for nuclear spin-dependent forces Spin Source:He spins at 20 atm.Spin direction reversed every 3 sec with Adiabatic Fast Passage2= 0.87K-3He co-magnetometerSensitivity: 0.7 fT/Hz1/2Uncertainty (1) = 18 pHz or 4.3·10-35 GeV 3He energy after 1 month (smallest energy shift ever measured)
22New limits on neutron spin-dependent forces Constraints on pseudo-scalar coupling:Limit on proton nuclear-spin dependent forces (Ramsey)Recent limit from Walsworth et alPRL 101, (2008)Limit from gravitational experiments for Yukawa coupling only (Adelberger et al)Present workG. Vasilakis, J. M. Brown, T. W. Kornack, MVR, Phys. Rev. Lett. 103, (2009)Anomalous spin forces between neutrons are:< 210-8 of their magnetic interactions< 210-3 of their gravitational interactionsFirst constraints of sub-gravitational strength!
23ConclusionsSet new limit on Lorentz and CPT violation for neutrons at 3×10-33 GeV, improved by a factor of 30Highest energy resolution among Lorentz-violating experimentsSearch for anomalous spin-dependent forces between neutrons with energy resolution of 4×10-35 GeV, first constrain on spin forces of sub-gravitational strengthSearch for CPT-even Lorentz violation with 21Ne is underway, limits maximum achievable velocity for neutrons (cn-c)~10-28Can achieve frequency resolution as low as 20 pHz, path to sub-pHz sensitivity, search for 1/MPl2 effects