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:
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+!... states, such 2 QCDpractitioners sum rules, was lattice the2 spectrum calculations4 and properties and so on.of the† Little low-lying attentionq hadronic was states, paid suchto highly " 2 c ! Im d x A{OT (Ox) 2}(0) 4A iqx= † as ρ mesons,Since theexcited pionsas incepti¯onρ mesons, and states. nucleons.of pions QCD TheO and till reason A nucleons. the number end is obvious: of A Millennium number of methods the of decay methodscO the was prime widthsd developed wasx interest developede of2 then o toexcTftheQCD totreatitedtreat(x states) such such(0) grown | | | | ! " | {O | O| ! }| "# "τA| {O O }| #∼ ∆ states,practitioners startingwithstates, from thec was starting the excitation2 the soft-pion spectrumd from4x e number, theiqx technique and soft-pionn propertiesT so that technique( whichx) they of† the(0) predates which overlap low-lying predatesn and QC had| collectivizeDbyadecade,then QC|ronicDbyadecade,then states, themselves, such and | O| " | {O OτA }| #∼ q ∆ QCD sumas ρ mesons, rules,couldQCD lattice pionsbe sum treated rules,! and calculations nucleons. as lattice continuum. calculations A and number so on. and of methods so Little on. Little attention was attention developed∆ was was paid to paidtreat∼toto such highly highly states, startingexcitedIn the from states. Regge the The soft-pion theory reason which technique is obvious: dominated which the decay predates high widths energy QC ofDbyadecade,then theory the excited before states QC growD, highly6 excited states. The reason is obvious: the decay widths of the excited" 2 states grow QCD sumexcitedwith rules, the states lattice excitation played calculations2 number, an4 important so andiqx that so they on. role Little overlap in phenomenological attention† and collectivize was paid the analysetomselves, highlys since and they with the excitation number,cO so thatd x theye overlapn T ( andx) collectivize(0) nA qq¯ the| A|mselves,A n andqq¯ n excited states.could be The treated reason| as| continuum. is! obvious: the" | decay{O widthsO of}| the"#∼ exc|ited∆| states#∼ grow" | | # could bewith treated the excitationIn as the continuum. Regge number, theory so which that they dominated overlap high and energy collectivize theory the beforemselves, QCD, and highly q ∆ 2 Incould the Regge beexcited treated theory states as continuum. which played dominated an important high role∼ energy in2 phenomenological theory before analyse QCsD, since highly they excited statesIn the played Regge theory an important which dominated role in high phenomenological energy theory before analyse QCsD, since highly they A qq¯ A 2 A n qq¯ n excited states played an important" role| | in#∼ phenomenological" | | # analyses since they determine the daughter Regge trajectories.2 The Regge theory gave rise to dual resonance models which eventually grew2 into string2 theory. Ironically, string theory that emerged from the dual resonance models shortly after became “string theory for nonhadrons,” and was elevated to the status of “theory of everything” in the 2 2 = uudddd O∆B=−2 i k qLα ,qRα˙ ,i,k=1, 2, 3 , α, α˙ =1, 2
∆B=−2 = uudddd " O qi ijk,qk ,i,k∆B=−2 ==1uudddd, 2, 3 , α, α˙ =1, 2 Lααβ Rα˙O qi " ,qk ,i,k=1, 2, 3 , α, α˙ =1, 2 Lα Rα˙ = uudddd α˙ β˙ O∆B=−2 i " k "ijk qLα ,qRα˙ ,i,k=1, 2, 3 , α, α˙ =1, 2 ∆I =1, 2, 3 ""ijkαβ αβ ∆B=−2 = uudddd ∆B=−2 = uudddd " α˙ β˙ O n n¯ i"ijk " k O qLα ,qR˙ α˙ ,i,ki =1, 2k, 3 , α, α˙ =1, 2 ↔ αβ "α˙ β q ,q ,i,k=1, 2, 3 , α, α˙ =1, 2 ∆I =2, 3 "∆I =1, 2, 3 Lα Rα˙ α˙ β˙ ∆" I n=1, 2n¯, 3 " τnn¯ ↔ ijk ∆I =1n, 2, 3 n¯ αβ ∆I↔=2, 3 " ∆B=−2 = uudddd"∆ijkB=−2 = uudddd p O O n ∆In¯ =2, 3 α˙ β˙ ↔ τnn¯ qi ,q"k ,i,kqi ,q=1k , 2,i,k, 3αβ, α, α˙ =1=1,,22, 3 , α, α˙ =1, 2 n ∆I =2, 3 Lα Rα˙ Lα Rα˙ " τnpn¯ ∆I =1, 2, 3 n¯ α˙ β˙ τnn¯ p " n n n¯ " " π+ p ↔ ijk ijk nn¯ ∆I =2, 3 αβ∆I =1, 2, αβ3 B, ∆B =2 n " " n¯ + π τ ˙ ˙ n¯ ! nn¯ "α˙ β n n¯ "α˙ β ∗ † c π+ n¯ c n = " u¯ γ5un B,"+ =∆B =2 p ↔ " | OO | # n¯ π| | τ B, ∆B =2nn¯ ! ∆I =1,∆2,I3 =2∆I,=13 , 2, 3 ∗ †B, ∆B =2c n An¯ cO n = " u¯n¯ γ5un " = ! " | ∗ O† | # c |!| τnn¯ n n¯ n n¯ n∗¯ c† n =c " u¯ γ5un " =n¯ ↔ τnn¯ ↔ 4 iqx n¯ c † On = " u¯ γ5un¯n " = d x e T ("x|)"OO| (0)|O# | =# cn¯q qq¯ A+ ...| | |τ | τnn¯ ! {O O } nnπ¯ + ∆I =2, 3 ∆I =2, 3 4 iqx A A † p d x e T (x) (0) = cq qq¯ + ... ! {O O }B,! ∆B =2 τnn¯ τnn¯ 2 4 4 d4iqxx eiqxT † (†x) †(0) = c qq¯ + ... 2 cO Im d x A dTx e (Tx) (x(0)) (0)A ==cq qq¯ +q ... ! n ! ! {O {OO O} } ∆B=−2 = uudddd | | ! " | {O O }|∗ #† τAO c ! p p 2 4 n¯ cO i n k=† " u¯n¯ γ5un " = 2 cO Im d x A T qL(αx,q) Rα˙ (0),i,kA=1=, 2, 3 , α, α˙ =1, 2 τA " | O | # ! ! | | τnn¯ The|2 average|2 4! 4 over" | neutron{O† O† state}| # τ nuc n n¯ n 2 c2O cOIm Imd xdAxT A T(x) (x(0)) A(0)= A = | | ! " | {O∆ O }| # Aτ"nucijk | | ! " | {O O }| # τnuc2 + αβ " τA = R τnn¯2 ,R4 =iqx † " 2 n¯ π n¯ cO d x e An!4T iqx(x) (0) n"† | 2| |2 | 4 iqx " d| x{Oe † T O (x)}| α˙(0)#∼β˙ "= cq qq¯ + ... cO 2d!x e4 niqxT! (x) (0){O†n O| "| } ∆ + + | |cO! d x"e | {On T O(x) }| (0)#∼n∆ | | π π | | ! " | {O O" 2 ∆}|I =1#∼, 2, 3 ∆ B, ∆B =2 2 4 iqx †q ∆ ! cO d x e n T (x) (0)∼ 2q n ∆ 4| | n n¯ B,† ∆B =2 B, ∆B =2 | | ! "where| {O EucledianO2 cO }| Im #∼ disx ∆aA relevantT ↔(x) hadronic(0) A = duality scale. ! | | ∼! " | ∆{OI =2∗, 3 O† }| # τAc n¯ cO n = " u¯n¯ γ5un ! " = ! Takingq ∆ A qq ¯ A A n qq¯ n for∗ theτAτ†nn¯ leading cOPE∗ † term wec get ∼ " | | #∼ " A| qq¯| #n¯AcO" |An On=qq|¯"n¯u¯#cn¯Oγ5unn ="" u¯=n¯ γ5un| | " τ=nn¯ " | O p| #A qq¯" A| OA| n# qq¯| |n τnn¯ | | τnn¯ ! | | "∼2 ! | ∆| " τA = R τ 16,Rn ! =| | "∼ ! A| | " nn¯ O A! A16 A A qq¯ A A n qq¯ n n¯ O " | | #∼ " | | 2 # 2 16 4 iqx4π+ iqx∆ 4=0† .iqx5GeV" 2 † † For O and an2 educated24 iqx∆d =0guessx ed.5GeVxT fore † ( xT d) x e(0) ( x T) = c((0)qxqq¯) +=(0)...cq=qq¯cq+qq¯ ...+ ... cO d x e n TB, ∆B(x=2) (0) n | | ! ! {O! {OO }22O{O−1 O} } | | ! " | {O O22R =4−}|1.!7#∼10∆ s R =4∗ † .7 c 10 s n¯ cO n = " u¯n¯ γ5un " = × 2 " | O | #q ×∆ | | τnn¯ ! ! 2 ∼ 4 2 4 † † ! 2 cO Im 2 dA x2 cAO T4Im (x)d x(0)A TA (=†x) (0) A = 2 cO Im d x A T (x) (0) A = what is close to the result| 4 | iqx obtained! † "| by|| {OFriedman,! O " |Gal}|{O # τOnuc }| # τnuc 1Introductiond x e| T | (x) (0)! = cq qq¯ +"... | {O O }| # τ (2008). ! {O 2O } nuc 1Introduction ! 2 2 Since the incepti¯on2 2 of4 QCD4 iqx till the† 2 end of4 Millenniumiqx† the prime" interest† oftheQCD" 2 cO Im d x A T (x) (0) A = | | |2 | | c|O ! d" |x{Oe OcOn }|T # dτ(Ax)e (0)n Tn (x) (0) n " The inclusivepractitioners approach| was |does the! spectrum2 includeτ |4" and| |alliqx! properties{O the mechisms.O of" the|}| low-lying{O#∼ † ∆O had ronic}| states,#∼ such∆ Since the incepti¯on of QCD till the endcO of MillenniumA d x e then T prime(x interest) (0) oftheQCDn | | as ρ mesons, pions and nucleons.2 ∆ A number of methods was developed to treat such | τA =|R τ! ,R= " | {O O }| #∼ ∆ practitioners was the spectrumstates, starting and from properties then soft-pionn¯ ofA! the technique low-lying which had predatesronic QC states,Dbyadecade,then such 2 7 as ρ mesons, pions andQCD nucleons. sum rules,2 A4 lattice numberiqx calculations of methods† and" so was on. developed Little attention to treat was paid suchto highly cO d x e n T (x) (0) n | | excited states.| | ! The reason" | {O isO obvious:}| #∼ the∆ decay widths of the excited states grow states, starting from the soft-pion techniqueq ∆ which predates QCDbyadecade,then QCD sum rules, latticewith calculations the excitation and number, so∼ on. so that Little they attention overlap and was collectivize paid to the highlymselves, and could be treated as continuum.2 excited states. The reasonIn the is obvious: Regge theory the which decay dominated widths high of the energy exc theoryited states before QC growD, highly with the excitation number,excited states so that played they an important overlap and role2 in collectivize phenomenological2 themselves, analyses and since they could be treated as continuum.determine the daughter Regge trajectories. The Regge theory gave rise to dual In the Regge theoryresonance which models dominated which eventually high energy grew into theory string before theory. Ironica QCD,lly, highly string theory that emerged from the dual resonance models shortly2 after became “string theory excited states playedfor an nonhadrons,” important and role was in elevated phenomenological to the status of analyse “theorys of since everything” they in the determine the daughter1980s Regge and early trajectories. ’90s. With this The promotion Regge the theory previous g interestave rise to ex tocited dual hadronic resonance models whichstates eventually faded away. grew At the into same string time, theory. in QCD highly Ironica excitedlly, string states we theoryre treated as that emerged from thebelonging dual resonance the the realm models of asymptotic shortly freedom after whichbecame inevitably “string qualifie theorydthemas “dynamically uninteresting objects.” for nonhadrons,” and wasThis elevated attitude changed to the in status recent of years “theory with the of advent everything” of string–ga inuge the duality 1980s and early ’90s.methods, With this based promotion on the ’t Hooft the previous limit [1] with interest the number to ex ofcited colors hadronicNc while 2 →∞ states faded away. Atg theNc sameis kept time, fixed. in In QCD this limit highly the excited meson decay states widths were tend treated to zero, as so that 1 belonging the the realmindividual of asymptotic highly excited freedom mesons becomewhich well-defined. inevitably qualifiedthemas “dynamically uninterestingThe objects.” string–gauge duality-based ideas predict a certain pattern for excited reso- nances. On the other hand, significant amount of data regarding excited mesonic This attitude changed in recent years with the advent of string–gauge duality 1 Baryons, if treated in the standard ’t Hooft procedure, defy this rule; their decay widths, methods, based on thegenerally ’t Hooft speaking, limit do not[1] vanish with in the the limit numberNc of, colors also theirN massesc grow aswhileNc.However, 2 →∞ →∞ the Nc limit exists for the mass differences, and experiments show that rather high excitations g Nc is kept fixed. In this→∞ limit the meson decay widths tend to zero, so that individual highly excitedof nucleons mesons and other become baryons well-defined. can be identified1 using the existing data. The string–gauge duality-based ideas predict a certain pattern for excited reso- nances. On the other hand, significant amount of data3 regarding excited mesonic
1 Baryons, if treated in the standard ’t Hooft procedure, defy this rule; their decay widths, generally speaking, do not vanish in the limit Nc , also their masses grow as Nc.However, →∞ the Nc limit exists for the mass differences, and experiments show that rather high excitations →∞ of nucleons and other baryons can be identified using the existing data.
3 PROTON DECAY
Proton is a topological non-trivial configuration of the pion field (Skyrmion) Decay of the proton is protected by topology Hybrid Skyrmion/bag model decay possible but exponentially suppressed due to tunneling (instanton) DISCUSSION
We calculated hadronic matrix elements including non-perturbative QCD effects resulting in suppression. This suppression can be sizeable. Drawback not a very stable calculation due to bag size. Where Lattice Can Help
✦ Is BSM running non-perturbative? - Model-dependent (assume pert. models for now)
✦ Is QCD running non-perturbative? - Should be checked (pert. running reasonable)
✦ What is neutron-antineutron matrix element? - Inherently non-perturbative question
✦ What is effect in nuclei? - Very interesting, VERY hard question Future Outlook Currently in progress:
✦ Independent analysis checks
✦ L = 20, 390 MeV pions
✦ L = 32, 240 MeV pions
Feasible in the next year or two:
✦ Physical Point Calculation
✦ Chiral Fermion Calculation NNbar suppression factor in nuclei: theory developments
A. Vainshtein: operator product expansion calculation in progress (with B. Kopeliovich) will implicitly include all processes and give independent estimate of size and error of Gal calculation.
M. Buchoff: lattice calculation of nnbar transition matrix element in progress, special structure of nnbar operator makes it possible, should make possible quantitative connection between nnbar limit and energy scale
M. Stavenga: Skyrme calculation of extra suppression of B violation from chiral dynamics?
ALSO (Vainshtein): ΔB=2 in nuclei can also come from “di-proton decay”, How does this affect limits form nnbar in nuclei? Vacuum N-Nbar transformation from bound neutrons:
Best result so far from Super-K in Oxygen-16
32 24 observed candidates; ! > 1.89!10 yr (90% CL) ! 16O 24.1 exp. background
! = R ! !2 nucl nn free
if R = 5 !1022s"1 (from Friedman and Gal 2008) 16O
8 #24 ! !(from bound) > 3.5"10 s or " < 2"10 eV !16 times higher than sensitivity of ILL expt.
ILL limit (1994) for free neutrons: ! > 0.86!108s nn Bound neutron N-Nbar search experiments
32 Experiment Year A n⋅year (10 ) Det. eff. Candid. Bkgr. τ nucl , yr (90% CL) Kamiokande 1986 O 3.0 33% 0 0.9/yr >0.43×1032 Frejus 1990 Fe 5.0 30% 0 4 >0.65×1032 Soudan-2 2002 Fe 21.9 18% 5 4.5 >0.72×1032 SNO * 2010 D 0.54 41% 2 4.75 >0.301×1032 Super-K 2011 O 245 12.1% 24 24.1 >1.89×1032
* Preliminary • From Kamiokande to Super-K atmospheric ν background is about the same ~ 2.5 /kt/yr.
• Large D2O, Fe, H2O detectors are dominated by backgrounds; LAr detectors are unexplored • Observed improvement is weaker than SQRT due to irreducible background and uncertainties of efficiency and background. • Still possible to improve a limit but impossible to claim a discovery. Super-Kamiokande Result 2000 (a) Signal MC 1500
1000 12 % detec on efficiency 500 sys. uncertainty 23% (mostly intranuclear sca ering) 20000 (b) Atmospheric neutrino MC 1500 24.1 background events 1000 ν osc. effects are included 500 sys. uncertainty 24% (mostly flux, cross sec ons) 20000
Total Momentum (MeV/c) (c) Data 1500 24 candidates 1000 T > 1.89 1032 years 500 bound ⇥ T 0 bound 0 250 500 750 1000 1250 1500 1750 2000 ⌧free = 23 1 1 10 s 2 r ⇥ Invariant Mass (MeV/c ) =2.4 108 s ⇥ Liquid Argon TPC Compared to Iron Calorimeters: - can do be er than requiring nch >= 4 Poten ally big gains in efficiency and Compared to WC BG rejec on! - can resolve recoil proton, charged current lepton
G. Karagiorgi, LBNE-docdb-5645 Observa ons v Proton decay detectors have a long history of studying nnbar. Usual quali es apply: large mass, high efficiency, low background v Analyses have been fairly crude so far. No modern MVA techniques. High background rate in water cherenkov is daun ng. v LAr TPC, even one as small as LBNE/10 kton should do very well. Let’s study! “Slow” Neutrons: MeV to neV n ν β Nuclear reactor/ 300K n Spallation source 235U 2MeV n 235U 0.1eV γ Neutron Moderator ν 30K (LH2, LD2) γ 103 n β 235 2 T30K U 10 T293K ~MeV neutrons from 101 fission or spallation, 100 ) n
E -1 thermalized in ~ 20 ( 10
W collisions in ~ 100 µs 10-2 T E λ v 10-3 neV meV (K) (meV) (A) (m/sec) 10-4
-5 UCN Very cold Cold ThermEpitherm 300 25 1.6 2200 10 10-6 -8 -7 -6 -5 -4 -3 -2 -1 0 20 2 6.4 550 10 10 10 10 10 10 10 10 10 En [eV] N-Nbar search at ILLSchematic (Heidelberg-ILL-Padova-Pavia layout of ) Heidelberg - ILL - Padova - Pavia nn search experiment at Grenoble 89-91 (not to scale) Cold n-source 25! D2 fast n, " background
58 HFR @ ILL Bended n-guide Ni coated, 57 MW L ~ 63m, 6 x 12 cm 2 H53 n-beam ~1.7. 1011 n/s Focusing reflector 33.6 m No GeV background No candidates observed. Flight path 76 m < TOF> ~ 0.109 s Measured limit for Detector: a year of running: Magnetically Tracking& shielded Calorimetry Discovery potential : 95 m vacuum tube N %t2 = 1.5%109 sec with L ~ 90 mn and t = 0.11 sec Measured limit : "18 Annihilation 7 measured Pnn&n
µBt<<ћ ILL achieved |B|<10 nT over 1m diameter, 80 m beam,one layer 1mm shield in SS vacuum tank, 1% reduction in oscillation efficiency (Bitter et al, NIM A309, 521 (1991). For new experiment need |B|<~1 nT
If nnbar candidate signal seen, easy to “turn it off” by increasing B
Voptt<<ћ: Need vacuum to eliminate neutron-antineutron optical potential difference. P<10-5 Pa is good enough, much less stringent than LIGO 2. ILL n-nbar beam line
Cold neutrons
Annihilation detector
Beam stop
Fermilab 18.06.2012 n-nbar at ILL 6 The conceptual scheme of antineutron detector
n + A → 〈5〉 pions (1.8 GeV) Annihilation target: ~100 thick Carbon film
annihilation 4 Kb nC capture 4 mb vertex precisely defined. No background was observed
Annihilation detector (INFN Padova and Pavia) 1. Inner Vertex Detector: 10 layers of Limited Streamer Tubes (LST), 0.3 g/cm3, Vertex 4 cm 2. Outer Calorimeter: 12 layers of LST interleaved with Pb/Al planes 3. Timing: Inner and outer planes of Plastic Scintillators (PSc), 700 ps, 4. Cosmic ray rejection with 95 m2 outmost layer of PSc, separated by 10 cm Pb.
60 000 electronic channels Overall nbar detection efficiency 522%.
Explosion-proof gas mixture
Fermilab 18.06.2012 n-nbar at ILL 26 Information from D. Dubbers, based on ILL Experiment
The <10 nT stated limit was conservative. ~1nT should be achievable with a very similar shielding approach. Need to also worry about 60 Hz
Vertex resolution of ILL nnbar detector was very coarse (~5 cm) compared to annihilation target thickness (~100 microns). Lots of room for even further background reduction.
Neutron backgrounds from slow neutron absorption/scattering on annihilation target can be (and needs to be) improved in new experiment to reduce tracker deadtime from MeV capture gammas
Vacuum chamber/B shielding of experiment still exists at ILL How to Improve the Experiment? Not so Easy. Max neutron flux/brightness: ~unchanged for ~4 decades
1E+18 US-SNS IBR-2 ISIS JSNS-1 HFIR ILL NRU MLNSC
/s) MTR 1E+15 2 FRM-II NRX HFBR SINQ-III SINQ-ISINQ-II X-10 1E+12 IPNS IBR-30 KENS Thermal Flux (n/cm 1E+09 CP-2 Tohoku Linac
CP-1 Berkeley 37 inch cyclotron 1E+06 Fux of pulsed Fissions reactor 0,35mCi Ra-Be source sources pulsed reactor continoues spallation source peak pulsed spallation source 1E+03 Trend line of reactorsl Trend of spallation sources (average) Chadwick average Trend of spallation sources (peak) 1E+00 Year 1900 1920 1940 1960 1980 2000 2020
Neutron flux is increasing only slowly with time R. Eichler, PSI Target Region Within Core Vessel
Target Module with jumpers
Outer Reflector Plug
Target Inflatable seal
Core Vessel water cooled shielding
Core Vessel Multi-channel flange
5 Managed by UT-Battelle for the U.S. Department of Energy Presentation_name Summary • The SNS is operating at a very high level of reliability and at times power levels > 1MW. • Development of high powered targets based on the SNS experience can be accomplished. • Cost savings are possible based on the SNS data. • Experienced personnel are available to help develop these high powered targets.
30 Managed by UT-Battelle for the U.S. Department of Energy Presentation_name Inverse cylindrical geometry (1)
6.6*107 UCN/s/100mA 800 MeV p+ 800 MeV p+ Heat load @ 100mA ≡ 80KW 53cm Total heat: 27.4 W Neutron heat: 17.2 W 40L-He Photon heat: 9.6 W Al(20K) Proton heat: 0.6 W W W 2.4*108 UCN/s/100W (heat in the He) H2 (75% ortho, 20K)
Bi(300K)
Cylindrical proton target (beam rastered around circumference) Cryogenic SESAME moderator meV neutrons
SANS pulsed proton linac MeV neutrons for Radiation Effects
Designed/built/characterized by graduate students Local user program in operation ~1MW Slow Neutron Source @Project X?
G. Greene: rough scaling from SNS+ straight guide->~1/4 ILL possible
T. Gabriel: project X source would be less $$$ than SNS, many benefits from SNS experience and ongoing ESS design
G. Muhrer: MCNP/vetted design for cold source with high kappa superfluid helium exists.
C. Liu (for D. Baxter): LENS neutron source at IU can be used to evaluate cold n moderator improvements (grooved moderators, nanoparticle reflectors,…) BetterBetter FreeFree NeutronNeutron ExperimentExperiment (Horizontal(Horizontal beambeam shown:shown: verticalvertical possible)possible) need slow neutrons from high flux source, access of neutron focusing reflector to cold source, free flight path of ~200m
Improvement on ILL experiment by factor of ~1000 in transition probability is possible with existing n optics technology (see G. Greene talk)
D ~ 2-3 m
L ~ 200 m
Possible improvements in sensitivity (Nt2)
•Intrinsic source brightness (assume 1MW) x 1/4
•Colder moderator (gain goes as λ2) x 2
•Coupling to experiment x 2
•Larger moderator face (30x30cm2 vs 6x12cm2) x 12
•Use “high-m” neutron reflector (assume m=6) x 36
• Longer experiment (200m vs 76m gain ~ L2 ) x 7
Estimated Sensitivity Gain ~3x103
Take away message: A substantial improvement is possible with only straightforward extension of existing technology Focusing o Can combine most of improvements; Super-m o CW or pulsed; Reflector L ~ 20m o Max UCN (<10 m/s) enrichment will be most advantageous;
o Cold and VCN are also used; Vacuum o Ultimate combination of all Tube and Mag. Shield improvements should boost L ~ L~100100 m m the sensitivity by factor > 1,000 u Dia dia~ 5 ~ m 4 m times several years of operation
1 2 hvtgt=+0 2 105 m = 100 m/s⋅+ 1 s 4.9 m/s222 ⋅ 1 s
105 m = 10 m/s⋅⋅ 3.7 s+4.9 m/s222 3.7 s Supermirror
non-uniformity and roughness decreases the reflectivity
2 2 exp(-k⊥ Rrms )
φc(Ni)/λ=1.7 mrad/Å m =φc/φc(Ni)=vc(Ni)/vc v⊥(Ni)=7 m/s
Date(2012/06/18) by(H.M.Shimizu) Title(Supermirrors) Conf(Project X Physics Meeting) At(Batavia, IL) page 4 m=4-7 Supermirrors http://www.swissneutronics.ch/
Supermirror: commercially available up to m=7 (v⊥=50m/s)
Date(2012/06/18) by(H.M.Shimizu) Title(Supermirrors) Conf(Project X Physics Meeting) At(Batavia, IL) page 17 Summary
Multilayer mirrors enhances the figure-of-merit of n-nbar experiments. Multilayer fabrication technology was remarkably improved in the past decade. monochromatic reflectors m≤10 Focusing of cold neutrons in vertical flight path supermirrors m≤7 Confinement of VCN Enhancement of VCN intensity substrateless supermirrors m≤5 Enhancement of VCN intensity
Date(2012/06/18) by(H.M.Shimizu) Title(Supermirrors) Conf(Project X Physics Meeting) At(Batavia, IL) page 29 Supermirror Optics
G. Greene: greatest single contributor to possibility of improved free neutron experiment
H. Shimizu: m=10 mulitlayer n momochromators exist, m=7 n supermirrors, exist, radiation damage can be handled using SM coating on metal, research on H and D-doped diamond-like carbon mirrors in progress
H. Shimizu: Nagoya U active x-ray mirror manufacturing group exists, available ~2015 for new project Groups in India
During May, 2011, a short workshop was organized by Dr. Amlan Ray in VECC, Kolkata on N-Nbar oscillation studies Several experts from USA participated in this event A group from VECC (Kolkata) led by Dr. Ray had a few discussions with the Nuclear and Particle physics groups at SINP (Kolkata) The 2 institutes jointly show interest in joining an activity on N-Nbar oscillation studies – P. Das, A. Ray, A.K. Sikdar at VECC – S. Banerjee, S. Bhattacharya, S. Chattopadhyay at SINP
June 18, 2012 Interest in the N-Nbar Oscillation Studies S. Banerjee 2 Free neutron nnbar search: relation with other project X ideas?
Technical:
B. Filippone: both nnbar and (one version of) nEDM can use bright slow neutron source: might one source feed both?
(someone in tracker session): detectors for mu2e experiment and kaon experiments share neutron-induced background issues with nnbar detector
Scientific:
Nnbar improvements squeeze post-sphaeleron baryogenesis. EDM experiments squeeze sphaeleron+EW-scale BSM physics. Do null measurements in both areas at Project X/elsewhere leave leptogenesis by default as the last viable baryogenesis mechanism? 3 Questions
1. How much better well could we do at Project X? MUCH BETTER... BUT NEED DETAILED SIMULATIONS
2.What would it cost? NEED PRELIMINARY ENGINEERING
3. Is it worth doing? NEED ANSWERS TO 1.& 2. PLUS THEORY
23 NNbar and Project X: What do we need (what will we have?) by Snowmass?
Theory: sharper understanding of nnbar in nuclei EFT analysis of all ΔB=2 operators involving standard model fields (preliminary) lattice calculations of nnbar matrix element
Experiment (underground detectors):
Calculation of ΔB=2 reach for underground liquid Ar detectors
Experiment (free neutrons):
Sensitivity/$$$ ratios for likely options NNbar NNbar SummarySummary
New physics beyond the SM can be discovered by NNbar search Improvement in free neutron oscilla on probability of a factor of ~1,000 is possible If discovered:
• n→nbar observa on would violate B‐L by 2 units, establish a new force of nature, illuminate beyond SM physics, and may help to understand ma er‐ an ma er asymmetry of universe
If NOT discovered: • will set a new limit on the stability of “normal” ma er via an ma er transforma on channel. Will constrain some scenarios for B‐L viola on and “post‐sphaeleron” baryogenesis SummarySummary
New physics beyond the Standard Model can be discovered by NNbar search
Experiments with free neutrons possess very low backgrounds (sharp vertex localiza on): ILL experiment observed no background. Interpreta on of result is independent of nuclear models. Any posi ve observa on can be turned off experimentally with the applica on of a small magne c field.
Sensi vity of free neutron experiment for NNbar transi on rate can be improved by factor of ~1000 using exis ng technology [Combina on of improvements in neutron op cs technology, longer observa on me, and larger‐scale experiment]. Further improvements in a free neutron experiment can comes from neutron op cs technology development.
US high‐energy intensity fron er complex could in principle provide the type of dedicated source of slow neutrons needed for NNbar experiment.