AXIONS AND AXION-LIKE PARTICLES

Transcription

1 AXIONS AND AXION-LIKE PARTICLES FRANK AVIGNONE th UNIVERSITY OF SOUTH CAROLINA COLUMBIA, SOUTH CAROLINA, USA 7 INTERNATIONAL WORKSHOP ON ULTRACOLD AND COLD NEUTRONS:PHYSICS AND SOURCES St. PETERSBURG, RUSSIA, JUNE 8-14,2009

2 CONTENTS THE STORY STARTS WITH QUANTUM CHROMODYNAMICS AND ENDS WITH COSMOLOGY THE STRONG CP PROBLEM AND THE NEUTRON EDM WHAT ARE PECCEI-QUINN AXIONS? WHERE DO THEY COME FROM? HOW DO WE SEARCH FOR THEM? HOW FAR HAVE WE GOTTEN? WHAT ARE AXION-LIKE PARTICLES (ALPs), HOW DO THEY DIFFER FROM PECCEI-QUINN AXIONS? TeV PHOTONS FROM AFAR,NEW COSMOLOGICAL MOTIVATIONS WHERE DO WE GO FROM HERE?

3 -26 NOW 2.9X10 e-cm

4 a neutron with an electric dipole moment violates both parity and time reversal symmetry. If CPT holds then CP is also violated. A violation of CP in QCD predicts an electric dipole moment for the neutron.

5 CP-VIOLATION IN THE EARLY UNIVERSE FROM THE ASYMMETRY BETWEEN MATTER AND ANTIMATTER IN THE UNIVERSE, A POPULAR HYPOTHESIS IS THAT THERE WAS A SIGNIFICANT CP- VIOLATION IN THE EARLY UNIVERSE. MEASURING A NEUTRON EDM MUCH LARGER THAN THE -32 STANDARD MODEL VALUE (10 e-cm), WOULD GIVE GREAT SUPPORT TO THAT HYPOTHESIS.

6 NEUTRON EDM MEASUREMENTS HOW FAR CAN ULTRACOLD NEUTRONS TAKE US?

7 THE BIRTH OF THE AXION IN 1977 ROBERTO PECCEI AND HELEN QUINN POSTULATED A NEW GLOBAL SYMMETRY IN QCD WHICH IS SPONTANEOUSLY BROKEN. Phys. Rev. Lett. 38,1440 (1977). THE GOLDSTONE BOSON FROM THIS BROKEN SYMMETRY ESSENTIALLY PLAYS THE ROLE OF A NEW TERM IN THE ACTION THAT CANCELS THE CP-VIOLATING TERM. (Steven Weinberg Phys. Rev. 40,223 (1977, and Frank Wilczek, Phys. Rev. Lett. 40, 279 (1977). THE AXION IS A GOLDSTONE BOSON; IT CAN INTERACT WITH PHOTONS, ELECTRONS AND WITH QUARKS!

8 AXIONS AND ALPs AXIONS ARE SPINLESS BOSONS THAT OBEY THE FOLLOWING: THESE ARE CALLED PECCEI-QUINN AXIONS! ALPs HAVE ALL THE SAME PROPERTIES BUT THEIR MASS AND COUPLING ARE NOT CONSTRAINED TO BE CONNECTED IN ANY SPECIAL WAY!

9 HOW DO WE SEARCH FOR AXIONS, WHAT ARE THE SOURCES? AXIONS CAN BE CREATED BY PHOTONS INTERACTING IN MAGNETIC FIELDS VIA THE PRIMAKOFF DIAGRAM! THEY CAN BE CREATED IN THE SUN! sun 0 nucleus THEY CAN INTERACT DIRECTLY WITH ELECTRONS PHOTONS AND QUARKS!

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11 0 THE PRIMAKOFF 2-PHOTON VERTEX DIAGRAM

12 THE MOST SENSITIVE EXPERIMENTAL SEARCH THUS FAR TRACKS THE SUN 1.5 hr DURING SUNRISE AND SUNSET +/- 8 DEGREES.

13 THE CERN AXION SOLAR TELESCOPE (CAST) 10 METER LONG LHC TEST MAGNET WITH A 9 TESLA MAGNETIC FIELD KONSTANTIN ZIOUTAS, U. PATRAS SPOKESMAN WHY CAN T WE JUST INCREASE THE LENGTH?

14 QUANTUM COHERENCE IN THE MAGNET WHEN THE AXION ENTERS THE B-FIELD IT BECOMES COHERENT WITH THE PHOTON! THIS LIMITS THE LENGTH OF THE MAGNET TO A COHERENCE LENGTH

15 SOLAX, COSME, DAMA

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17 ARE AXIONS OR ALPs GOOD CANDIDATES FOR COLD DARK MATTER? YES! COLD AXIONS LEFT OVER FROM THE BIG BANG ARE BEING SEARCHED FOR IN RESONANT RF-CAVITIES IN THE ADMX EXPERIMENT.

18 LOW MASS AXIONS COULD BE COLD DARK MATTER SIKIVIE ALSO SUGGESTED SEARCHING FOR CDM AXIONS WITH TUNED RESONANT CAVITIES, THE ADMX EXPERIMENT.

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20 A MICROWAVE CAVITY IS TUNED BY INSERTING A DIELECTRIC TUNING ROD INTO IT. WHEN THE FREQUENCY CORRESPONDS TO THE AXION ENERGY, THERE WILL BE RESONANT ABSORPTION.

21 THE ADMX EXPERIMENT HAS NOW MOVED TO THE UNIVERSITY OF WASHINGTON, SEATTLE FROM LAWRENCE LIVERMORE NATIONAL LABORATORY.

22 PECCEI-QUINN AXIONS

23 SEARCH FOR AXIONS WITH Ge DETECTORS BRAGG-COHERENT PRIMAKOFF CONVERSION IN SINGLE CRYSTALS R.J. Creswick et al., Phys.Lett. B 427,235 (1998) F.T. Avignone et al, Phys. Rev. Lett.81, 5068 (1998) AXIONS CREATED IN THE SUN BY THE PRIMAKOFF EFFECT ARRIVE ON EARTH VERY WELL COLLIMATED BECAUSE THEY COME FROM THE SOLAR CORE THAT IS A VIRTUAL POINT. THEY IMPINGE ON A Ge DETECTOR WITH A KNOWN SINGLE CRYSTAL STRUCTURE, KNOWN ORIENTATION AND KNOWN LOCATION ON EARTH.

24 GERMANIUM HAS A DIAMOND STRUCTURE, AND DETECTOR CRYSTALS ARE GROWN ALONG THE [100] AXIS. AS THE LINE OF SIGHT TO THE SUN SATISFIES A BRAGG COHERENCE CONDITION, CONVERSION OF AN AXION IN THE ELECTRIC FIELD OF THE NUCLEUS IS ENHANCED, RESULTING IN A PREDICTABLE MODULATION IN THE SIGNAL. R.J. CRESWICK et al., Phys. Lett. B 427 (1998) 235.

25 PHYSICS POTENTIAL A CAREFUL AND COMPLETE ANALYSIS CONCLUDES THAT A 1-TON EXPERIMENT, WITH VERY LOW BACKGROUND, COULD ACHIEVE A SENSITIVITY OF A COUPLING OF 10 GeV or SLIGHTLY BETTER. NICE, BUT NOT SUPERIOR TO CAST FOR LIGHT AXIONS. WHAT IS SO SPECIAL ABOUT LIGHT MASS ALPs? WE WILL SEE!

26 MASSIVE AXION SEARCH WITH A GAS IN THE MAGNET. P-Q AXION MODELS

27 Annals of Physics 323,2851 (2008) laser axion photon photon detector axion 2-photon Primakoff Diagram

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29 A COSMOLOGICAL PUZZLE HOW DO TeV PHOTONS ARRIVE TO EARTH AFTER TRAVELING COSMOLOGICAL DISTANCES? HOW DO THEY ESCAPE THE OPACITY OF THE BATH OF BACKGROUND RADIATION? THEORETICALLY THEY SHOULD BE SEVERELY ATTENUATED BY PHOTON - + PHOTON PRODUCTION OF e e _ PAIRS!

30 THE ALP HYPOTHESIS A SOLUTION TO THE PROBLEM WAS CONSIDERED BY De ANGELIS, RONCADELLI, AND MANSUTTI, AND MODIFIED BY SIMET, COOPER AND SERPICO PROPOSES THE FOLLOWING SCENARIO: ARD, Phys Rev. D 76, (2007) SCS, Phys. Rev. D 77, (2008) TeV photons are produced in the AGN and convert to ALPs in the strong local magnetic fields, The photons pass through the background radiation (acting like the wall), Then they reconvert to photons in the magnetic fields of the Milky Way

31 A SIMILAR COSMOLOGICAL PUZZLE WHAT IS THE REASON THAT ACTIVE GALACTIC NUCLEI (AGNs) ARE SO MUCH DIMMER OPTICALLY THAT THEY THEORETICALLY SHOULD BE? C. Burrage, A-C Davis, D.J. Shaw Phys. Rev. Lett. 102, (2009) Active Galactic Nuclei Shed Light on Axion Like Particles. AGN ONE EXPLANATION IS THAT PHOTONS RADIATING FROM THE AGNs PASS THROUGH STONG MAGNETIC FIELDS OF THE AGN AND CONVERT TO AXION-LIKE PARTICLES (ALPs). WHEN THEY ARRIVE AT THE MAGNETIC FIELD OF THE MILKY WAY, THE DISTANCES AND FIELD STRENGTHS COULD BE ALOT LESS AND THE ALPs DO NOT CONVERT BACK AS READILY.

32 THE CONVENTIONAL WISDOM IS THAT THE COUPLING OF THE ALPs TO THE MAGNETIC FIELDS CAN NOT BE VERY MUCH WEAKER THAT CURRENT CAST BOUNDS OR CONVERSION WILL BE TOO SUPPRESSED TO MAKE THIS MECHANISM WORK. THE UNCERTAINTIES IN THE MAGNETIC FIELD STRENGTHS IN THE AGNs AND IN THE MILKY WAY DO NOT ALLOW AN ACCURATE ESTIMATE OF HOW STRONG THAT COUPLING SHOULD BE! THE MASS OF THE AXION MUST BE VERY MUCH LESS THAN THE PQ-AXION WITH COUPLINGS AS LARGE AS NEEDED, SO THAT THE AXION AND PHOTON MAINTAIN COHERENCE OVER VERY LONG DISTANCES!

33 R. BERNABEI et al., arxiv: [astro-ph] 17 April The DAMA/LIBRA Collaboration.

34 SEARCH FOR WINTER-SUMMER MODULATION IN DAMA/LIBRA From the DAMA/LIBRA Data (2008)

35 CALCULATIONS USING THIS IS AN ORDER OF MAGNITUDE BETTER THAN THE EARLIER DAMA RESULT WHICH HAD REACHED A POINT OF DIMINISHING RETURNS. THIS EXPERIMENT HAS A RATHER HIGH BACKGROUND. A FACTOR OF TEN REDUCTION WOULD BE REQUIRED.

36 THE CURRENT BOUNDS C. Hagmann, H. Murayama, G.G. Raffelt, L.J. Rosenberger, and K. van Bibber 2008 Rev. Part. Physics. Phys. Lett. B 667,1 (2008).

37 WHERE ARE WE; WHERE DO WE GO FROM HERE? CAST IS THE MOST SENSITIVE EXPERIMENT TO DATE! THE SEARCH FOR PQ-AXIONS ABOVE MICRO- EV IS HITTING A WALL!! Creswick, Nussinov,& Avignone, Phys. Rev. D 78, (2008). LARGE SCINTILLATOR ARRAYS, OR Ge DETECTOR ARRAYS WILL BE COMPETITIVE IF BACKGROUNDS ARE REDUCED FAR BELOW 1 count/kev/kg/day IN THE 2-10 kev ENERGY RANGE. LIQUID Xe AND Ar SCINTILLATORS COULD ALSO BE EFFECTIVE!

38 CONCLUSIONS THE EXISTENCE OF AXION-LIKE PARTICLES COULD EXPLAIN TWO VERY INTERESTING PUZZLES IN COSMOLOGY. THESE ALPs MUST BE VERY LIGHT TO MAINTAIN COHERENCE WITH THE PHOTON COMPONENT OF THE WAVE FUNCTION OVER LONG DISTANCES! NEW LARGE DETECTOR ARRAYS OPERATING OVER LONG PERIODS OF TIME MAY BE SENSITIVE ENOUGH TO PROBE THE RELEVANT PARAMETER SPACE. OPERATING CAST AGAIN WITH NO GAS FILL MIGHT BE THE ANSWER. SOME THOUGHT SHOULD BE GIVEN TO A SuperCAST VERSION.