Testing lepton flavour and lepton number violation at ATLAS

Transcription

1 Testing lepton flavour and lepton number violation at N. Gökhan Ünel - UCI on behalf of Collaboration ATL-PHYS-SLIDE January 2010 FLAVLHC-09, CERN December 14 th -16 th, 2009

2 Outline 2 - generalities LHC time table - what we expect Motivations for LFV / LNF Possible channels & previous studies τ μ γ SuSY & Sugra models 2HDM model Double Charged Higgs LR symmetric models Outlook

3 Detector Overview 3 Had Calo Inner Detector EM Calo Muon chambers EndCap Toroid Forward Calo Barrel Toroid coils Solenoid weigth= Tons length= 44 m diameter= 22 m Mag field = 2 Tesla

4 Experiment status 4 In most of 2009, recorded cosmic rays which were used for calibration & alignment. has started taking beam data all sub-detectors are active, providing data collisions s=2.36tev are recorded. Display of a 2-jet candidate with uncalibrated ET of 23GeV & 16GeV and η of -2.1 & 1.4, respectively. collisions with stable s=900gev are being recorded.

5 LHC Schedule initial period: late 2009: first s = 0.9 TeV 2010 s = 7 TeV, later s = 10 TeV 2011 s = 14 TeV L=1.2x10 33 cm -2 s -1, expect 10 fb -1 /year, =low luminosity 5 nominal runs (after 2011): L = cm -2 s -1, expect 100 fb -1 /year, =nominal luminosity Ultimately, L = 2.3x10 34 cm -2 s -1 (cryo limited) SLHC (after 2020?): L = cm -2 s -1, expect 1000 fb -1 /year

6 LFV Motivations 6 Atmospheric/Solar/Accelerator/Reactor experiments all favor Neutrino Oscillations K2K, accelerator: ν µ ν τ Phys.Rev.Lett.94:081801,2005 Kamland, Reactor: ν e ν x SK2, Atmospheric: ν µ ν τ SNO, Solar: ν e ν x

7 more motivations 7 Lepton Flavor Conservation is not a true requirement of the SM! mixing? mixing. mixing! The same for Lepton Number Conservation if charge conservation can be satisfied or for Majorana fermions.

8 LFV diagrams 8 EW theory from neutrino oscillations: if LFV exists, SM: τ τ w ν τ Z/h ν μ w μ μ μ μ ɣ BABAR collaboration Phys. Rev. Lett. 95 (2005) BR (τ± μ±γ) < 6.8x10 90% CL arxiv: (2009) BR (τ± μ±γ) < 4.4x10 90% CL Belle Collaboration arxiv: , proceedings of leptonphoton 2007 & EPS 2007 BR(τ ± μ μ ± μ ± ) < 3.2x10 90% CL if LFV and beyond SM exist: τ ν χ h/h/a χ τ μ μ ɣ PDG-04 τ µγ < τ eγ < τ µµµ < Z eµ < Z µτ < Z eτ <

9 LNV diagrams 9 new particles could give rise to LNV e.g. doubly charged Higgs, Δ ++ decaying leptonically Δ ++ l + l + Majorana Neutrino (N) is its own anti-particle N decay gives LNV 50% of the time

10 some signal channels 10 W τν τ Z ττ B τν τ X Eur.Phys.J. C14, 319, 2000 τ μ μ μ τ sources τ μ γ χ 2 χ 1 τ μ H/A τ μ μ e γ not feasible large e background/ small mixing μ e e e τ e e e

11 τ µ γ 11 Source: q q W τν τ BR(τ µγ) < 10 6 Background from FSR & Radiative production: W µ ν µ +γ W τν τ µ ν µ ν τ +γ generator cuts: η (γ&µ) < GeV/c < p T (µ) 20 GeV/c < E T (γ) analysis cuts: 0.08 < ΔR 6 GeV/c < p T (µ) < 20 GeV/c -phys/ background events Pythia + Photos + Fast smearing was used. signal events low luminosity 17 bg events/year for m τ <8 signal events/year

12 Assume 6x6 slepton mass matrix : susy -1 ẽ L, µ L, τ L,ẽ R, µ R, τ R 12 Phys. Rev. D 63, (2000) LFV strength: δ = M2 τµ M 2 L LF breaking Term Consider msugra: m 0 =100GeV m 1/2 =300GeV A 0 =300GeV tan(β)=10 sgn µ=+ Chirality breaking Term if: δ 0 mixing we have µ in τ 1 χ o 2 τ 1 µ τ 1 χ o 1 τ τ 1 χ o 1 µ if: δ=0 m χ 0 1 =122GeV m χ 0 2 =228GeV m l L =232GeV m l R =156GeV m τ1 =145GeV m τ2 =233GeV BR BR( χ 0 2 τ 1 τ)=66% BR( χ 0 2 µ R µ)=12%

13 susy Phys. Rev. D 63, (2000) Signal: Emiss μ τhad j pp q q q χ 0 2 q χ 0 2 qqµτ χ 0 1 µτ χ 0 1 Selection cuts: N j 4 1P T > 100GeV 3P T > 50GeV M e f f E T miss + ΣP T > 800GeV E T miss>0.2m e f f η <2.5 R>0.4 Backgrounds: SM background is very small Normal SuSY signal becomes background to LFV in SuSY χ o 2 ττ χ o 1 µ τν µ ν τ χ o 1 isajet + fast simulation + realistic smearing + full tau low luminosity How can we extract the LFV events?

14 susy Phys. Rev. D 63, (2000) LFV gives harder mass distribution and more muons compared to nonlfv decay: χ o 2 ττ χ o 1 µ τ ν µ ν τ χ o 1 χ o 2 ττ χ o 1 e τ ν e ν τ χ o 1 nolfv sign & flavor subtraction to remove background E N(µ ± τ ) N(e ± τ ) in case of nonlfv, expect E = 0. We can do a counting experiment. LFV For 10fb -1 & BR=0.1 E = 476 ± 39. or if 5σ signal is -1 BR=0.023 or δ ~ 0.1 or δ < 0.1 BR< 10-9

15 2HDM Phys. Rev. D 67, (2003) Type III 2HDM: LFV tree level BR(A o /H o τµ)=κ 2 τ,µ( 2m µ m τ )BR SM (H o ττ) κ µ τ 1 compatible w/ μ g-2 results g o o A /H μ g Considered Backgrounds: W ± Z µ ± ν µ τ + τ W + W µ + ν µ τ ν τ tt µ ± ν µ τ ± ν τ bb Z(γ ) τ + τ µν µ ν τ τ W ± + jets µ ± ν µ + jets A o /H o τ + τ µν µ ν τ τ τ Signal Signal Final states: Hadronic final state: τ jet, isolated μ & missing ET Leptonic (e) final state: hadron activity, isolated e, μ & missing ET

16 2HDM Phys. Rev. D 67, (2003) σ bg is 10 4 σ signal Cuts: Pythia + fast simulation, 30 fb -1 Selection optimized for LFV mode:

17 2HDM Phys. Rev. D 67, (2003) signal is well in the reach of LHC/: MA(GeV) s/ B combined Significance ma GeV if signal, 95% CL can be obtained after few years of low luminosity

18 LNV J. Phys. G 32 (2006) Doubly charged Higgs, single production in Left Right symmetric models m WR >640GeV assuming equal left/right gauge couplings: g=0.64 fast MC L=100fb -1 /yr Selection e/μ in η <2.5 & ε reco =90% p l T>50 & p j1 T>200 & p j2 T>200 η j1 -η j2 >2 SM Background min 10 events required m W R =650GeV j! + + " W +,! + W +, l + j signal σ in fb l + reach with 100(a) & 300(b) fb -1

19 LNV arxiv: v4, ("CSC book") CERN OPEN LR symmetric model w/ W R & N majorana Full MC used (14TeV) LO σ(pp W R X); W R lnl ll jj 24.8pb (W R =1800,Ne=Nµ=300GeV) (a) 47.0pb (W R =1500,Ne=Nµ=500GeV) (b) Baseline Selection pt 20 GeV, η l <2.5, η j <4.5, SM Background tt, Z/γ & vector boson pair production + multijets for l=e Lepton sign investigated after this publication. discovery limits a:150pb 1 & b:40pb 1

20 Summary & Outlook 20 is currently running to record collision data LFV is studied within SM and via BSM Yearly yields to discover LFV susy: exp 476 ± 39 vs bg 0 2HDM: 3.4 < S/ B < 93 SM-like: exp 46 ± 2 vs bg 1 or push BR(τ μɣ) limit to lower values LNV studied in BSM models Δ ++ mass up to 1.8TeV depending on W + mass Early discovery possible in LR models, but SS vs OS lepton comparisons not public. Some of these analyses shown can be also done with 200 pb -1 at s=10tev (the results are not yet public)

21 Thank you for listening 21 Further references Neutrino oscillation papers K2K: hep-ex/ , Phys.Rev.Lett.94:081802,2005 Phys.Rev.Lett.100:221803,2008 Kamland: hep-ex/ , Phys.Rev.Lett.94:081801,2005 arxiv: Phys.Rev.Lett.100:221803,2008 Current LFV limits (thanks to S. Banerjee) BaBar: arxiv: (2009), BR (τ± μ±γ) < 4.4x10 90% CL Belle: arxiv: (2007), BR(τ ± μ μ ± μ ± ) < 3.2x10 90% CL J.Ellis et.al. Eur. Phys. J. C14, 319, (2000). public web pages : Backup slides

22 τ µ γ 22 Source: Z ττ Compared to W channel, 10x less signal 1 tau for tagging, other for signal generator cuts: cosθ < 0.5(Mz) P T miss < 60GeV N jet < < m(τγ) < 3.0GeV analysis cuts: p µ T > 6 GeV (e,γ) > 15 GeV E µ T selection efficiency ~14% E. Barberio unpublished Pythia + Photos + Atlas Fast simulation was used. Studied Backgrounds: W µνγ W τν γ τ µν µ ν τ Z µ + µ γ Z τ + τ γ τ µν µ ν τ tt γ bb γ low luminosity 1.6 < M < 2.0 GeV ~12 bg events/year for m τ ~10 signal events/year

23 & CMS detectors 23 CMS length x diameter (m) 44 x x 15 Magnetic Field (Tesla) 2 4 Weight (Tons) eta coverage 2.7>muons, 2.5>tracking 4.9>calo 2.4>muons, 2.5>tracking 5.0>calo Inner detector Silicon pixels, Silicon strips, Transition Radiation Tracker. Silicon pixels, Silicon strips. Electromagnetic Calo Hadronic Calo Muon System Lead plates as absorbers with liquid argon as the active medium Iron absorber with plastic scintillating tiles as detectors in central region, copper and tungsten absorber with liquid argon in forward regions. Large air-core toroid magnets with muon chamber form outer part of the whole Lead tungstate (PbWO4) crystals both absorb and respond by scintillation Stainless steel and copper absorber with plastic scintillating tiles as detectors Muons measured already in the central field, further muon chambers inserted in the magnet return yoke

24 susy - details 24 same flavor ll diff flavor ll SM

25 τ µ γ details 25 kinematic distributions W µ ν µ γ τ µ γ W τν τ µ ν µ ν τ γ