Neutron- An+neutron Oscilla+ons at the European Spalla+on Source by Camille Theroine

Transcription

1 NeutronAn+neutron Oscilla+ons at the European Spalla+on Source by Camille Theroine

2 Spalla:on process Technical Design Report, execu:ve editor: S. Peggs Fast neutrons Thermal/cold neutrons Ion source Proton Beam H 2 0 Neutron Beam Accelerator H 2 W Target Moderator

3 The European Spalla:on Source : ESS At ESS, the neutrons will be produced by spalla:on process. ESS will produce first neutrons in 2019 ESS will be the world s best source of neutrons: ESS peak brightness is 30x higher than ILL, the world s best research reactor Parameters Value* Number of target stations 1 Number of moderators 2 Number of instruments in construction budget 22 Number of beam ports 48 Separation of ports 5 Annual operating period 5000 h Reliability 95% The :meaveraged slow neutron brightness between ESS and ILL is comparable 5x more intense than SNS, the world s most powerful spalla:on source * Technical Design Report, execu:ve editor: S. Peggs 2013.

4 Road to realizing ESS with 6 instruments Ini:al opera:ons

5 European Joint Ownership ESS construc+on cost ~ 1843 M Current members preparing their construc+on commitments - Sweden, Denmark, and Norway (~50% total) - France, Germany, and the United Kingdom (~30% total) - Italy, Spain, Switzerland, Netherlands (~>15% total) - Czech Republic, Hungary, Poland, Bal:c countries (~>5% total) Discussions with countries that would join aber construc+on start - Belgium, Finland, Israel, Portugal, Russia, Singapore..? ICHEP, 29 July 2014 Valencia, Spain

6 ESS Science drivers Exis:ng pulsed neutron sources deliver short pulses, because the emphasis at the :me of their construc:on was on higher energy neutrons (100 mev to 1,000 mev) (TDR). Long pulse + low repe::on rate of the proton pulses = ESS ideal source for neutrons with energies in the range of about 0.1 mev to 50 mev. Science priori:es have evolved. à e.g current trends in condensed majer sciences (sok majer and life science, magne:sm and engineering materials) stress the importance of slow dynamics and large- scale fluctua:ons of mul:component systems. ESS addresses these scien:fic trends by focusing on cold and thermal neutrons, in part by adop:ng a longpulse :me structure (TDR). Cover by 22 instruments! (include in the ESS construc:on budget)

7 Fundamental ESS Many ques:ons remains : Why more majer than an:majer? is there a unifica:on of forces (superforce)? What is the nature of the dark majer?. Two complementary ways: The energy fron+er: based on measurements of par+cle interac+ons in collisions of highest possible energy, aiming to the produc:on of new heavy elementary par:cles CERN). The precision fron+er: look carefully at lowenergy processes that can be accurately predicted by the SM. The differences from expecta:ons in such processes would prove the existence (and give informa:on) on the form of new physics.

8 High precision fron:er physics Standard Model of par:cle physics (SM) Precision experiments Beyond SM Gravity New interac:ons Neutron decay : e.g Life:me Neutron an:neutron oscilla:ons Proper:es of the neutrons : e.g nedm Gravita:on level spectroscopy

9 High precision fron:er physics Standard Model of par:cle physics (SM) Precision experiments Beyond SM Gravity New interac:ons Neutron decay : e.g Life:me Neutron an:neutron oscilla:ons Proper:es of the neutrons : e.g nedm Gravita:on level spectroscopy

10 NeutronAn:neutron oscilla:ons Neutron An+neutron Neutrons in vacuum and low magne:c field spontaneously conver:ng to an:neutrons = : Mass, electric charge, spin : quark à B = 1 for neutron and B = 1 for an:neutron To observe a nnbar oscilla+on : ΔB = 2 B has to be violated by 2 units Observa:on of viola+on of baryon number is one of the most important ques:on of par:cle physics to explain mareran+marer asymmetry or BAU

11 Physics case Nature of baryon number viola+on ² it is required for explana:on of BAU (Sakharov) Sakharov proposed [ a set of three necessary condi:ons that a baryongenera:ng interac:on must sa:sfy to produce majer and an:majer at different rates. These three Sakharov condi:ons" are: Baryon number viola:on. Csymmetry and CPsymmetry viola:on. Interac:ons out of thermal equilibrium. Baryon number viola+on ² Exists in the Standard Model but suppressed at low temperatures and (BL) is conserved ² Mo:vated by GUT models (Glashow, Pa: ) Qualita:ve different: B viola:on but (BL) conserva:on (proton decay to leptons) B viola:on and (BL) viola:on (nnbar) ΔB = 1 (proton decay) ΔB = 2 (nnbar) compare Majorana neutrinos ΔL = 2

12 Physics case : summary nnbar may help to understand: Nature of baryon number viola:on Origin and nature of neutrino masses Nature of supersymmetric theories nnbar can probe intermediate energy scales, between the electroweak scale and grand unified theories. Origin of the majer in the Universe More specific models Observa+on of nnbar oscilla+ons new force of nature leading to the new physics beyond the SM No observa+on of nnbar oscilla+ons constrain certain models for new physics

13 NeutronAn:neutron oscilla:ons : phenomenology u u α: mixing strength between neutron and an:neutron d d Neutron α d d An:neutron " H = $ # E +V α α E V % ' & α = 0 in the Standard Model, V : poten:al difference for neutron and an:neutron Transi+on probability α 2 # α 2 +V 2 P n n = α 2 +V 2 sin2 % $! & t ( ' Transi+on probability (quasifree condi:on) # P n n = % α $! t & ( ' 2 = t 2 2 τ n n FoM (sensi+vity) : N n x t 2 with t free observa+on +me Current direct search limit ILL: α ev à free oscilla+on +me τ > 8.6 x 10 7 s. (Baldoceolin et al. (1994))

14 Previous experiment : ILL Experimental results = 1 ILL sensi:vity unit No oscilla:ons observed Upper limit reached aker a year of running τ nnbar > 0.86x10 8 s <t> s N 1.25x10 11 n/s No background FoM = N x <t 2 > = 1.5x10 9 n.s = 1 ILL sensi:vity unit M. BaldoCeolin et al. Z. Phys., C (1994)

15 nnbar ESS? Observe neutrons propaga:ng in free space for a maximum of :me without wall collisions wide beam port Long direct flight path (> 200m) Detector Large moderator for high integral flux Hornshaped supermirror reflector with a high m High vacuum < 10 5 Pa Magne:c fields shielded down to < 10nT + must be protected from radia:on Quasi free condi:on : ESS will be a green field facility FoM (sensi+vity) : N n x t 2 Interest for ESS : possibility to op+mize the facili+es during the design phase.

16 Requirements for a nnbar experiment Increase +me of flight Slow neutrons (increase t) Long free flight path Improved magne:c shielding to respect quasifree condi:on Increase the number of neutrons High flux source and op:misa:on star:ng from moderator Big phase space acceptance of neutron focusing reflector Progress in supermirror technology Long running :me (more than 1 year) No background Fast neutrons from spalla:on source discard by :me structure Timing and track reconstruc:on to limit events to target foil Suppression of MeV gammas from neutron capture by trigger Muon veto Result in large sensi:vity gain over previous ILLbased experiment

17 nnbar ESS ESS offers the possibility of performing a new search for free neutron oscilla+ons à improvement of the FoM : the sensi:vity should be ~500x ILL experiments Establish a collabora+on 1 st nnbar CERN last June à Find partners, ins:tu:ons can join at will à iden:fy the different working groups : experiment op:misa:on, cost es:mate 5 working groups have been formed Find funding Aim for full proposal to ESS in ~2 years? à Submission to ESS à Submission to funding agencies

18 Conclusions New physics beyond the SM can be discovered by nnbar Neutron-Anti-Neutron Oscillations at ESS June 2014, CERN, Geneva, Switzerland Sensi:vity can be improved by a factor ~ 500 : as combina:on of improvements in neutron op:cs technology/moderator development. ESS can provide the cold neutron source needed for a greatly improved free nnbar oscilla:on experiment. Neutral particle oscillations have proven to be extremely valuable probes of fundamental physics. Kaon oscillations provided us with our first insight into CP-violation, fast Bs oscillations provided the first indication that the top quark is extremely heavy, B oscillations form the most fertile ground for the continued study of CP-violation, and neutrino oscillations suggest the existence of a new, important energy scale well below the GUT scale. Neutrons oscillating into antineutrons could offer a unique probe of baryon number violation. Organising committee: G. Brooijmans (Columbia University) S. Chattopadhyay (Cockroft Institute) R. Hall-Wilton (European Spallation Source) Y. Kamyshkov (University of Tennessee) E. Klinkby (Technical University of Denmark and European Spallation Source) M. Lindroos (European Spallation Source and Lund University) L. Mapelli (CERN) nnbar collabora:on is forming : 1 st nnbar CERN last June The construction of the European Spallation Source in Lund, with first beam expected in 2019, together with modern neutron optical techniques, offers an opportunity to conduct an experiment with at least three orders of magnitude improvement in sensitivity to the neutron oscillation probability. At this workshop the physics case for such an experiment will be discussed, together with the main experimental challenges and possible solutions. We hope the workshop will conclude with the first steps towards the formation of a collaboration to build and perform M. Mezzetto (INFN Padova) H. M. Shimizu (Nagoya University) W. M. Snow (Indiana University) T. Soldner (Institut Laue Langevin) C. Theroine (European Spallation Source) Register before 19 May on the experiment.

19 Thank you! Monolith liner June 12, 2014 Steel shielding Vision