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Neutron scattering and extra interactions.

Neutron scattering and extra interactions. Guillaume Pignol Valery Nesvizhevsky Konstantin Protasov. Rencontres des particules 2008 LAPTH. The institute Laue-Langevin in Grenoble. Mountain. European Synchrotron. The ILL : Nuclear core 53 MW The most intense neutron

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Neutron scattering and extra interactions.

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  1. Neutron scattering and extra interactions. Guillaume Pignol Valery Nesvizhevsky Konstantin Protasov Rencontres des particules 2008 LAPTH

  2. The institute Laue-Langevin in Grenoble Mountain European Synchrotron • The ILL : • Nuclear core 53 MW • The most intense neutron source in the world

  3. Optical and Ultra Cold Neutrons (UCN) n matter • Ultra Cold Neutrons • energy < Fermi potential • total reflection at surfaces Can be stored in bottles E • Optical neutrons • wavelength >2 Å • interaction with bulk matter described by a mean potential (Fermi potential) ~ 100 neV 10 MeV production Thermal neutrons 0.025 eV Optical neutrons 100 neV Ultra Cold Neutrons velocity < 7 m/s

  4. Slow neutrons and fundamental interactions • Free neutrons feel all interactions very weakely • Weak interaction • β decay: 886 s • Strong interaction Fermi potentials ~100 neV • Electromagnetism No electric charge B = 1 T induce Zeeman split of ~100 neV • Gravity 1 m fall: neutron increases its energy by ~100 neV Neutrons can be very sensitive to new interactions!

  5. 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 Modification of gravity

  6. 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 Modification of gravity

  7. Slow neutron scattering with extra interaction Slow neutron Atom E < 1 eV • Coherent scattering length (Fermi) • Isotropic • Energy independant • Scales as ~ A1/3 • Not isotropic • Energy dependant • Scales as ~ A

  8. 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 A1/3 • Random depth.

  9. 1 Simple nuclear model + extra interaction We repeated the analysis with an extra force included Additional parameter Random potential model

  10. 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-1scattering amplitude one actually measures The two methods for measuring the scattering lengths do not bear the same sensitivity to extra force

  11. 2 Comparing forward and backward scattering No difference is observed for the nuclei for which both measures exist

  12. 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 eV one actually measures This idea first appeared in Leeb and Schmiedmayer, PRL 68 (1992)

  13. 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 eV, electromagnetic effects have to be taken into account.

  14. 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

  15. 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)

  16. 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

  17. Sensitivity to extra short range interactions neutron 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

  18. Spin dependant extra short range interactions neutron 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

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