Neutron scattering and extra interactions Guillaume Pignol Valery

Neutron scattering and extra interactions. Guillaume Pignol Valery Nesvizhevsky Konstantin Protasov Rencontres des particules 2008 LAPTH Guillaume Pignol (LPSC) Neutrons and extra interactions 23/01/2008 1

The institute Laue-Langevin in Grenoble Mountain European Synchrotron The ILL : § Nuclear core 53 MW § The most intense neutron source in the world Guillaume Pignol (LPSC) Neutrons and extra interactions 23/01/2008 2

Optical and Ultra Cold Neutrons (UCN) Optical neutrons § wavelength >2 Å § interaction with bulk matter described by a mean potential (Fermi potential) ~ 100 ne. V 0. 025 e. V 100 ne. V production n Thermal neutrons Ultra Cold Neutrons Guillaume Pignol (LPSC) Optical neutrons 10 Me. V matter Ultra Cold Neutrons § energy < Fermi potential § total reflection at surfaces Can be stored in bottles E velocity < 7 m/s Neutrons and extra interactions 23/01/2008 3

Slow neutrons and fundamental interactions Free neutrons feel all interactions very weakely § Weak interaction β decay: 886 s § Strong interaction Fermi potentials ~100 ne. V § Electromagnetism No electric charge B = 1 T induce Zeeman split of ~100 ne. V § Gravity 1 m fall: neutron increases its energy by ~100 ne. V Neutrons can be very sensitive to new interactions! Guillaume Pignol (LPSC) Neutrons and extra interactions 23/01/2008 4

Extra short range interaction We assume a new interaction between neutron and nucleus with A nucleons Mediated by a new light boson of mass M High Energy Physics Guillaume Pignol (LPSC) Neutrons and extra interactions Modification of gravity 23/01/2008 5

Extra short range interaction If a new boson gets its mass by a «Higgs mechanism» at the Electroweak scale: If the new boson travels in large flat extra dimensions (ADD) the coupling is suppressed. High Energy Physics Guillaume Pignol (LPSC) Neutrons and extra interactions Modification of gravity 23/01/2008 6

Slow neutron scattering with extra interaction Slow neutron Atom E < 1 e. V Coherent scattering length (Fermi) § Isotropic § Energy independant § Scales as ~ A 1/3 Guillaume Pignol (LPSC) § Not isotropic § Energy dependant § Scales as ~ A Neutrons and extra interactions 23/01/2008 7

1 Simple nuclear model We aim to exclude a contribution ~A in the set of measured scattering lengths Random potential model Peskhin, Ringo, Am. J. Phys. 39 (1971) § Square well potential for nuclear interaction § Radius R x A 1/3 § Random depth. Guillaume Pignol (LPSC) Neutrons and extra interactions 23/01/2008 8

1 Simple nuclear model + extra interaction We repeated the analysis with an extra force included Random potential model Guillaume Pignol (LPSC) Additional parameter Neutrons and extra interactions 23/01/2008 9

2 Comparing forward and backward scattering Slow neutron Atom Interference measurement Bragg diffraction measurement § Measurements using interference method sensitive to the forward scattering amplitude one actually measures § Measurements using Bragg-diffraction method sensitive to q = 10 nm-1 scattering amplitude one actually measures The two methods for measuring the scattering lengths do not bear the same sensitivity to extra force Guillaume Pignol (LPSC) Neutrons and extra interactions 23/01/2008 10

2 Comparing forward and backward scattering No difference is observed for the nuclei for which both measures exist Guillaume Pignol (LPSC) Neutrons and extra interactions 23/01/2008 11

3 Comparing forward scattering and total X-section Slow neutron Atom § Measurements using optical method sensitive to the forward scattering amplitude one actually measures § Measurements using transmission method sensitive to the total cross-section at 1 e. V one actually measures This idea first appeared in Leeb and Schmiedmayer, PRL 68 (1992) Guillaume Pignol (LPSC) Neutrons and extra interactions 23/01/2008 12

3 Comparing forward scattering and total X-section Very precise measurements exist for both methods, on lead and bismuth nuclei. No deviation is observed There is a hidden difficulty: for scattering at 1 e. V, electromagnetic effects have to be taken into account. Guillaume Pignol (LPSC) Neutrons and extra interactions 23/01/2008 13

Measuring asymmetry of scattering Diluted noble gaz Possible dedicated experiment § Forward/Backward asymmetry of scattering at noble gaz as a probe of new interactions § Can detect asymmetry of 10 -3 Must take into account Doppler thermal effect § Guillaume Pignol (LPSC) Neutrons and extra interactions 23/01/2008 14

Conclusions § Neutron constraints on extra interactions are several orders of magnitude better than those usually cited in the range 1 pm 5 nm. § We provided several independant strategies: neutron constraints are reliable. § Dedicated experiment (asymmetry of scattering) can easily improve the constraints by one order of magnitude. For the detailed analysis, see hep-ph/0711. 2298 (accepted in Phys Rev D) Guillaume Pignol (LPSC) Neutrons and extra interactions 23/01/2008 15

Quantum reflection of UCN Measured reflectivity agrees with Q. M. simplest calculation (Koester 1986 as an example) Ultra Cold Neutrons § velocity < 7 m/s § wavelength > 50 nm § Elastic reflection 99. 99 % § 10 -4 inelastic reflection at phonons § 10 -5 inelastic reflection at surface nanoparticles § 10 -5 absorption Guillaume Pignol (LPSC) Neutrons and extra interactions 23/01/2008 16

Sensitivity to extra short range interactions neu tron MIRROR New light boson of mass M New interaction between the neutron and the mirror with range monopole-monopole coupling spin-independant Modification of the spectrum Guillaume Pignol (LPSC) Neutrons and extra interactions 23/01/2008 17

Spin dependant extra short range interactions neu tron MIRROR New light boson of mass M New interaction between the neutron and the mirror with range monopole-dipole coupling Spin-dependent Different spectrum for spin up and spin down neutrons Guillaume Pignol (LPSC) Neutrons and extra interactions 23/01/2008 18