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Neutron-Antineutron Oscillation Experiments Neutron-AntineutronNeutron-Antineutron OscillationOscillation Experiments:Experiments: WhatWhat HaveHave WeWe LearnedLearned atat thethe Workshop?Workshop? W. M. Snow Indiana University/CEEM Project X Workshop Why ΔB=2? (theory/phenomenology) Neutron-antineutron oscillations in nuclei:theory and experiment Free neutron oscillations: experimental requirements @Project X Thanks to co-conveners: Chris Quigg (FNAL), Albert Young (NC State) Neutron-AntineutronNeutron-Antineutron Oscillations:Oscillations: SpeakerSpeaker ListList (from(from Germany,Germany, Georgia,Georgia, India,India, Japan,Japan, US)US) Speaker Subject R. Mohapathra, Maryland theory/phenomonology M. Snow, Indiana various G. Greene, ORNL/Tennessee R&D needs I. Gogoladze, Bartol/Delaware theory/phenomonology M. Chen, Irvine leptogenesis K. Babu, Oklahoma State theory/phenomonology M. Stavenga, FNAL theory M. Buchoff, LLNL theory/lattice E. Kearns, Boston experiment/nnbar in nuclei A. Vainshtein, Minnesota theory/nnbar in nuclei Y. Kamyshkov, Tennessee experiment options R. Tayloe, Indiana detectors K. Ganezer, CSUDH nnbar in nuclei D. Dubbers, Heidelberg ILL experiment T. Gabriel, ORNL/Tennessee SNS 1MW target G. Muhrer, LANL 1MW target/moderator design H. Shimizu, Nagoya neutron supermirror optics C-Y Liu, Indiana (also for D. Baxter, Indiana) moderator experiments/simulations S. Banerjee, Tata Institute detectors Neutron-Antineutron Oscillations: Formalism " n% ! = n-nbar state vector α≠0 allows oscillations #$ n&' " En ( % H = $ ' Hamiltonian of n-nbar system # ( E n & p2 p2 En = mn + + Un ; En = mn + + Un 2mn 2mn Note : • ( real (assuming T) • mn = mn (assuming CPT) U U in matter and in external B [ n n from CPT] • n ) n µ( ) = *µ( ) Neutron-Antineutron transition probability # E + V ! & ! 2 + ! 2 + V 2 . For H = P (t) = * sin2 - t 0 % E V ( n)n 2 2 $ ! " ' ! + V ,- ! /0 where V is the potential difference for neutron and anti-neutron. "23 Present limit on ! 1 10 eV Contributions to V: <Vmatter>~100 neV, proportional to density <Vmag>=µB, ~60 neV/Tesla; B~10nT-> Vmag~10-15 eV <Vmatter> , <Vmag> both >>α 2 2 " ! 2 + V 2 % * ! - * t - For t <<1 ("quasifree condition") P t $ ' n(n = , ) / = , / $ ! ' + ! . + 0 nn . # & 2 Figure of merit= NT N=#neutrons, T=“quasifree” observation time How to Search for N-Nbar Oscillations Figure of merit for probability: 2 N=total # of free neutrons observed NT T= observation time per neutron while in “quasifree” condition When neutrons are in matter or in nucleus, n-nbar potential difference is large->quasifree observation time is short B field must be suppressed to maintain quasifree condition due to opposite magnetic moments for neutron and antineutron (1) n-nbar transitions in nuclei in underground detectors (2) Cold and Ultracold neutrons εnn π Nucleus A A* + n nN pions π Why is it important to search for NNbar ? n Many reasons to believe that baryon number (B) is not a good symmetry of nature : Sphalerons in SM , GUTs, origin of matter etc. n If B is violated, important to determine the selection rules: B=1 (p-decay) or B=2 (NNbar) ? i) What is the scale at which B- symmetry is broken ? NNbar à lower scale physics than usual p-decay ii) NNbar oscillation intimately connected to neutrino mass physics when combined with quark-lepton unification Questions for N-N-bar oscillation n Are there decent (predictive?)theories explaining small neutrino masses which give observable N- N-bar oscillation ? n Implications of observable N-N-bar for cosmology i.e. does it affect conventional explanations of origin of matter/can it explain itself ? n Two examples of models for NNbar: (i) TeV scale Seesaw +Quark-Lepton unif. (ii) SO(10) GUT scale seesaw+TeV sextets New Particles at LHC: Color sextet scalars Δqq n TeVColor sextets are an inherent part of both models ; Can be searched at LHC: (I) Single production: ud → Δud → tj xsection calculated in (RNM, Okada, Yu’07;) resonance peaks above SM background- decay to tj; n Important LHC signature: σ (tt) > σ (tt ) (II) Drell-Yan pair production qq → G → Δud Δud n Leads to tjtj final states: LHC reach < TeV (Chen, Rentala, Wang; Berger, Cao, Chen, Shaughnessy, Zhang’10; Han, Lewis’09) Origin of matter and neutron oscillation n Current scenarios: (i) Leptogenesis; Related to seesaw; but hard to test ! (ii) Electroweak baryogenesis : Mhiggs <127 GeV; m ˜ 120 GeV (puts MSSM under tension) t ≤ n New scenarios: (Babu’s talk) (iii) Post sphaleron Baryogenesis both connected (iv) GUT baryogenesis to NNbar osc. 11 n Non-observation of NNbar upto 10}sec.will rule out simple models for PSB as well as the particular SO(10) model. Summary and Conclusions Conclusions • origin of matter: one of the great mysteries in particle physics and cosmology • leptogenesis: an appealing baryogenesis mechanism connected to neutrino physics • various leptogenesis mechanisms: • standard leptogenesis: gravitino problem, incompatible with SUSY • resonance leptogenesis • Dirac leptogenesis • While there is no model-independent way to test leptogenesis, searches at neutrino experiments (leptonic CPV, neutrino-less double beta decay) can provide supports for/distinguish among the mechanisms • neutron-antineutron oscillation: complementarity test • if observed ⇒ low scale leptogenesis scenarios preferred Mu-Chun Chen, UC Irvine Leptogenesis Fermilab Project X Study, 06/18/201220 B violation theory: What did we learn? R. Mohapathra/K. Babu/I. Gogoladze: models exist which give nnbar oscillations within range of improved experiments. Such models tend to possess rather specific structures and also produce signatures at LHC K. Babu: “post-sphaeleron” baryogenesis possibility (which can only be Δ B=2) is NOT ruled out experimentally. Present models tend to make observable LHC predictions. K. Babu/R. Mohapathra: Effective field theory analysis of all d=9, ΔB=2 operators in progress (not done before!), might make possible more model- independent statements. M. Chen: "standard" leptogenesis has some problems already! "Resonant" leptogenesis and Dirac leptogenesis also possible (latter since sphaelerons only couple to left-handed components). NNbar possibility is complementary to leptogenesis. Leptogenesis is very difficult to confirm experimentally. 8 Suppression of n→nbar in intranuclear transitions ! ! Neutrons inside nuclei are "free" for the time: !t ~ ~ ~ 4.5 "10#22s Ebinding 30MeV $ '2 & !t ) each oscillating with "free" probability = & ) & ) % !nn ( 1 and "experiencing free condition" N = times per second. !t $ '2 $ ' 1 & !t ) & 1 ) Transition probability per second: PA " = & ) "& ) ! & ! ) %& !t () A % nn ( !2 Intranuclear transition (exponential) lifetime: ! = nn = R "!2 A #t nn 1 where R~ ~ 4.5 "1022s!1 is "nuclear suppression factor" #t Actual nuclear theory suppression calculations for 16O,2 D,56 Fe, 40Ar by C. Dover et al; W.Alberico et al; B.Kopeliovich and J. Hufner, and most recently by Friedman and Gal (2008) corrected this rough estimate within a factor of 2 Theoretical nuclear NNbar u u suppression model is incomplete d α d α Usual d d approach q α 4q All these processes → q include the same amplitude α Suggested by S. Raby (2011) and result in the same indistinguishable final state n (of ~ 5 πs) →α ! 's Existing intranuclear NNbar limits need to be re-evaluated n J. Basecq and L. Wolfenstein (1983) = uudddd O∆B=−2 i k q ,q ,i,k∆B=−2 ==1∆uuddddB=,−22,=3 ,uuddddα, α˙ =1, 2 ∆B=−2 = uudddd Lα Rα˙ O O O i k i k i k q ,q ,i,k=1q, L2α, 3,q, α,Rα˙α˙ =1,i,k, 2 =1, 2, 3 , α, α˙ =1, 2 qLα ,qRα˙ L,i,kα Rα˙ =1, 2, 3 , α, α˙ =1, 2 "ijk ∆B=−2 = uudddd ∆B=−2 = uudddd " O αβ "ijk ijk i k ""ijkO qLαi ,qRα˙ k,i,k=1αβ , 2, 3 , α, α˙ =1, 2 αβ q ,q ∆,i,kB=−2 =" uudddd=1, 2, 3 , α, α˙ =1,"2 Lα ROα˙αβα˙ β˙ i k "" ˙ q ,q ,i,k=1α˙ β˙, 2, 3 , α, α˙ =1, 2 "α˙ β Lα Rα˙ ˙ " "α˙ β "ijk ∆I =1, 2, 3 "ijk ∆I αβ=1, 2, 3 ∆I =1, 2, 3 "ijk ∆∆BIn==1−2 =,n¯2uudddd, 3 "αβ n n¯ O nαβα˙ β˙ n¯ i k ↔ " ↔ ↔ q ,q ,i,kn =1n¯ , 2, 3α˙,βα˙ , α˙ =1, 2 Lα Rα˙ ∆I =2,∆3Iα˙ β=2˙ " , 3 ∆I =2, 3 ↔∆I =1" , 2, 3 ∆I =2, 3 τnn¯ τnn¯∆I∆=1Iτ=1n, n¯2, 3, 2, 3 "ijk n n¯ ↔ p τnn¯αβ n npn¯ n¯ p" ∆I ↔=2↔, 3 ∆I =2, 3 n p"α˙Estimateβ˙ ∆In=2, 3 n τnn¯ τnn¯n¯ n¯ Let us try to use∆ someI n=1 ,kind2, 3 τ ofnn¯ duality to find a relation n¯ p + π+ π between the free n n¯ + n¯ oscillationn p and nuclear stability. π↔ n B, ∆B =2 ∆πI+=2, 3 ! ∗ † n¯ c n ! n¯ B,c ∆nB==2" u¯ γ5un ∗" =† c O τ +n¯ n¯ c n = " u¯ γ5un " = " | O | #nn¯ π + |O| τnn¯ n¯ π n¯ " | !!O | # | | τnn¯ ∗ †† cc p wheren¯ cO decreasesnn == ""u¯u¯ γ γ B, 5 uu n ∆ B =2 + " " =. = A " | O O | # n¯n¯B,5 n∆Bπ=2| | " | O | # | | ττnnn¯n¯ ! ∗ † n c 4 iqx ! † Operator productn¯ c nexpansion= " u¯ γ5un d" x=e T (x) (0) = c qq¯ + ... " |∗ OO† | A# B,nc¯ ∆B =2| | q 1Introductionn¯ cO n =n¯ " u¯n¯ γ5un ! " =τnn¯ {O O } " | O | # | | τnn¯ ! 4 iqx ∗ † †+ c ! Since the incepti¯ond x e ofT QCDn¯ c ( tillx) thenπ (0) end= "A of=u¯ Millenniumγcq5uqq¯n2+ ... the" prime=4 interest oftheQCD† O n¯ 2 cO Im d x A T (x) (0) A = ! " {O| O O| # } | | τnn¯ 1Introductionpractitioners was the spectrum and properties| of| the low-lying! " had| ronic{O states,O such}| # τA 1Introductiond4x eiqxT (x) †(0) = c qq¯ + ... as ρ mesons,The average pions and over nucleons. a nucleus A number A of gives methods qits waslifetime! developed τ A to treat such 2 ! 4 {O O† } Since the incepti¯onstates,2 c starting ofO QCDIm from tilld the thex endA soft-pionT of Millennium( techniquex) (0) which theA prime predates= interest QCDbyadecade,then oftheQCD 1IntroductionSince the incepti¯on of QCD4 tilliqx the end of Millennium the prime interest oftheQCD practitioners was the| spectrum| ! andd" propertiesx|e {OT ofO(x the) low-lying(0)}| #= c hadτqqnuc¯ ronic+!..
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