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Vadim Rusu Fermilab Flavor Oscillations The last oscillation: mu2e at Fermilab Vadim Rusu Fermilab Flavor oscillations Maybe the most important feature of the SM why are 3 families anyway? Quarks change flavor (CKM), neutral leptons change flavor (MNS) Do charged leptons oscillate? (CLFV) answer: BNL Seminar Vadim Rusu - The last oscillation: mu2e 2 Flavor oscillations Maybe the most important feature of the SM why are 3 families anyway? Quarks change flavor (CKM), neutral leptons change flavor (MNS) Do charged leptons oscillate? (CLFV) answer: YES BNL Seminar Vadim Rusu - The last oscillation: mu2e 2 ✴ anomaly in muon g-2 (?) Hagiwara et al: hep-ph/0611102 Neutrinos have mass + + µ µ eγ→ e γ γ → W˜ µ e ν˜µ ν˜e 6 BNL Seminar Vadim Rusu - The last oscillation: mu2e 3 ✴ anomaly in muon g-2 (?) Hagiwara et al: hep-ph/0611102 Neutrinos have mass + + µ µ eγ→ e γ γ → W˜ µ e ν˜µ ν˜e 2 2 3α ∆m1i 54 6 BR(µ e⇥) = U ⇥ U < 10− → 32⌅ µi ei M 2 i=2,3 W ⇥ BNL Seminar Vadim Rusu - The last oscillation: mu2e 3 ✴ anomaly in muon g-2 (?) Hagiwara et al: hep-ph/0611102 Neutrinos have mass + + µ µ eγ→ e γ γ → W˜ µ e ν˜µ ν˜e 2 2 3α ∆m1i 54 6 BR(µ e⇥) = U ⇥ U < 10− → 32⌅ µi ei M 2 i=2,3 W ⇥ - not going to measure this one soon BNL Seminar Vadim Rusu - The last oscillation: mu2e 3 History CLFV: not a new idea In fact, almost everyone looked for this 1 10-1 10-3 10-5 10-7 10-9 10-11 10-13 10-15 10-17 10-19 1940 1950 1960 1970 1980 1990 2000 2010 2020 2030 BNL Seminar Vadim Rusu - The last oscillation: mu2e 4 History CLFV: not a new idea In fact, almost everyone looked for this 1 μ discovered in 1936 10-1 10-3 10-5 10-7 10-9 10-11 10-13 10-15 10-17 10-19 1940 1950 1960 1970 1980 1990 2000 2010 2020 2030 BNL Seminar Vadim Rusu - The last oscillation: mu2e 4 History CLFV: not a new idea In fact, almost everyone looked for this 1 μ discovered in 1936 10-1 10-3 Feinberg 1958 loop calculation μ→eγ ~ 10-4-10-5 10-5 10-7 10-9 10-11 10-13 10-15 10-17 10-19 1940 1950 1960 1970 1980 1990 2000 2010 2020 2030 BNL Seminar Vadim Rusu - The last oscillation: mu2e 4 History CLFV: not a new idea In fact, almost everyone looked for this 1 μ discovered in 1936 10-1 10-3 Feinberg 1958 loop calculation μ→eγ ~ 10-4-10-5 10-5 -7 Non observation of μ→eγ 10 (implies two neutrinos) 10-9 10-11 10-13 10-15 10-17 10-19 1940 1950 1960 1970 1980 1990 2000 2010 2020 2030 BNL Seminar Vadim Rusu - The last oscillation: mu2e 4 History CLFV: not a new idea In fact, almost everyone looked for this 1 μ discovered in 1936 10-1 10-3 Feinberg 1958 loop calculation μ→eγ ~ 10-4-10-5 10-5 -7 Non observation of μ→eγ 10 (implies two neutrinos) 10-9 Best limit so far 10-11 10-13 10-15 10-17 10-19 1940 1950 1960 1970 1980 1990 2000 2010 2020 2030 BNL Seminar Vadim Rusu - The last oscillation: mu2e 4 History CLFV: not a new idea In fact, almost everyone looked for this 1 μ discovered in 1936 10-1 10-3 Feinberg 1958 loop calculation μ→eγ ~ 10-4-10-5 10-5 -7 Non observation of μ→eγ 10 (implies two neutrinos) 10-9 Best limit so far 10-11 -13 mu2e10 intends to improve 10-15by 10000 and then 100 more w/ Project X 10-17 10-19 1940 1950 1960 1970 1980 1990 2000 2010 2020 2030 BNL Seminar Vadim Rusu - The last oscillation: mu2e 4 New physics Supersymmetry Compositeness Leptoquark MLQ = rate ~ 10-15 Λ ~ 3000 TeV 1/2 2 c 3000 (λμdλed) TeV/c ~χ 0 i - µ- e- µ d ~~ - lj lj - µ e L LQ qqq q d e- Heavy Neutrinos Second Higgs Doublet Heavy Z’ Anomal. Z Coupling 2 -13 g(H ) ~ 10-4g(H ) |UμNUeN| ~ 8x10 μe μμ 2 MZ’ = 3000 TeV/c - N - e - µ e µ- e- H t W µ- - e tt γ,Z,Z’ qqqqq q also see Flavour physics of leptons and dipole moments, arXiv:0801.1826 and Marciano, Mori, and Roney, Ann. Rev. Nucl. Sci. 58, doi:10.1146/annurev.nucl.58.110707.171126 BNL Seminar Vadim Rusu - The last oscillation: mu2e 5 Model independent Andre deGouvea (TeV) Λ B(μ→ e conv in 27Al)=10-17 4 10 κ << 1 κ >> 1 Mu2e B(μ → e conv in 27Al)=10-16 magnetic moment type four-fermion interaction operator MEG Upgrade µN → eN rate many µ → eγ rate ~300X MEG GOAL B(μ → eγ)=10-13 orders of magnitude µN → eN rate greater than µ → eγ rate 3 10 MEGMEGA 2011 SINDRUM II highermassscale EXCLUDED (90% CL) -2 -1 2 10 10 1 10 10 loop-dominated κ contact-dominated BNL Seminar Vadim Rusu - The last oscillation: mu2e 6 Muon to electron conversion µ+ → e+γ Time scale for entire process ~μs μ BNL Seminar Vadim Rusu - The last oscillation: mu2e 7 Muon to electron conversion µ+ → e+γ Time scale for entire process ~μs μ muons captured on target formation of atomic muon BNL Seminar Vadim Rusu - The last oscillation: mu2e 7 Muon to electron conversion BNL Seminar BNL muons captured on target on captured muons normalization immediately (~ps) falls to 1s (X rays) rays) (X 1s to falls (~ps) immediately formation of atomic muon atomic of formation µ + → e + γ Vadim Rusu - The last oscillation: mu2e oscillation: last The - Rusu Vadim Mu2e Proposal → Mu2e Proposal X Rays X μ Figure 1.1: Massive neutrino contribution to the charged lepton flavor-violating muon decay µ eγ. νi are neutrino mass eigenstates, while entire for scale Time Uαk, α = e, µ, τ and k = 1, 2, 3, are the → ~ process elemenFigurets of1.1:theMassivleptone neutrinomixing matrix.contribution to the charged lepton flavor-violating muon decay µ eγ. νi are neutrino mass eigenstates, while Uαk, α = e, µ, τ and k = 1, 2, 3, are the → 7 elements of the lepton mixing matrix. μ physics at or even above the TeV scale, regardlesss of its connection to neutrino masses. Concrete examples will be discussed in the next subsection. phAmongysics attheordievffenerenabtoCLFVve the Tchannels,eV scale,threeregardlessrare mofuonits connectionprocesses standto neutrinoout, thanksmasses. in Concretepart to theexamplesmuon’s willsmallbemassdiscussedand longin thelifetime:next subsection.µ eγ, µ eee and µ e- → → → conversionAmongin thenuclei.differenCurrent CLFVt expchannels,eriments threehave rarebeenmableuon proto rulecessesout,standat out,the 90%thanks in part to the m+uon’s +small mass and long lifetime: µ eγ10, µ11 [19eee] andandµµ+ e- confidence level, µ e γ with branching ratios above 1.→2 − → → + + → 12 able×to rule48out, at the→4890% e econ−eversionwith brancin nuclei.hing ratiosCurrenabtovexpe 1.erimen0 10−ts ha[20v].e Thebeenrate for µ− + Ti e− + + + × 11 → + Ticonfidencenormalizedlevtoel,theµ capturee γ ratewith (brancµ hinge conratiosversionabinovetitanium),1.2 10−is constrained,[19] and µ + + → → 12 12 × 48 →48 at ethee−90%e withconfidencebranchinglevratiosel, to abbeolessve 1.than0 104−.3 [2010].−The[21rate], whilefor µ−that+ forTi µ e− +e × × 13 → → conTiversionnormalizedin goldtois theconstrainedcapture toratebe(µless thane con7version10− in[22titanium),, 23]. Theisconcurrenconstrained,t → × 12 explorationat the 90%of allconfidencethree rarelevmel,uonto bproe lesscessesthanis of4.3the utmost10− [21imp], whileortancethatgivforen thatµ e × 13 → conversion in gold is constrained to be less than 7 10in−distinct[22, 23w].ays.TheIfconcurrenCLFV t the three process “feel” different types of new physics× is observexplorationed in ofanally onethreeof rarethesemuonprocesses,processesresultsis offromthe utmostother searcimportancehes willgivplaeny thata fundamenthe threetal prorolecessas far“feel”as establishingdifferent typthees ofnaturenew ofphtheysicslepton-flain distinctvor violatingways. If newCLFV physics.is observed in any one of these processes, results from other searches will play a fundamenDependingtalonroletheasnaturefar as establishingof the CLFVthephnatureysics, oneof theof lepton-flathe threevorboundsviolatinglistednew abophveysics.turns out to be the most significant. For a particular class of models, including severalDepof endingthe standardon the supnatureersymmetricof the CLFVones, pheffysics,orts tooneobservof thee µthreeeγboundsprove listedto → be abmostove turnspromisingout tocurrenbe thetlymostandsignificanin the immediatet. For a particularfuture. TheclassMEGof models,experimenincludingt several of the standard supersymmetric ones, efforts to observe µ toeγµ proveeγ to [24], currently taking data at PSI, is ultimately aiming at being sensitiv→e 14 →eriment brancbe hingmostratiospromisinglarger currenthan sevtlyeralandtimesin the10−immediate. However,future.given theTheexistenceMEG expof very intense[24], currenfuturetlymuontakingsources,data µat PSI,e-conis vultimatelyersion willaiminglikely servat beeingas thesensitivdeepeesttoprobµ e eγ → 14 → of CLFV,branchingsupratioserior tolargerµ thaneγ insevitseralnewtimesphysics10− reac. Hoh wregardlessever, givenofthetheexistencenature ofofthevery intense future muon sources,→ µ ise-conthisv“feature,”ersion willwhiclikelyh willservbeeasdiscussedthe deepinestmoreprobe new physics. Among other factors,→it of CLFV, superior to µ thateγ indrivitsesnewus tophconcenysics reactrateh regardlesson the CLFVof thepronaturecess whereof the detail in the next subsection,→ a nnewuclear-capturedphysics. Amongmuonotherconvfactors,erts intoitanis thiselectron“feature,”— µ whice-conh willversionbe discussedin nuclei.in more → detailNegativin elythe nextchargedsubsection,muons thatthat drivstopesinus tomatterconcenaretratequiconklythetrappCLFVedproandcessformwhere a nuclear-captured muon converts into an electron — µ etil-contheversionmuoninisninuclei.the muonic atoms, which undergo electromagnetic transitions→un 1s orbital.NegativTrappely edchargedmuonsmeitheruons Micthathel-decastop iny ormatterconvertareinquicto neutrinoskly trappinedtheandfieldform muonic atoms, which undergo electromagnetic transitions until the muon is in the 1s orbital. Trapped muons either Michel-decay or convert into neutrinos in the field 4 4 Muon to electron conversion BNL Seminar BNL nucleus (~4fm) nucleus the Bohr radius is 20fm 20fm is radius Bohr the muons captured on target on captured muons normalization immediately (~ps) falls to 1s (X rays) rays) (X 1s to falls (~ps) immediately formation of atomic muon atomic of formation µ + → e + γ → Vadim Rusu - The last oscillation: mu2e oscillation: last The - Rusu Vadim muon sees sees muon Mu2e Proposal → Mu2e Proposal X Rays X μ Figure 1.1: Massive neutrino contribution to the charged lepton flavor-violating muon decay µ eγ.
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