Search for Supersymmetry at LHC

Transcription

1 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 1/40 Search for Supersymmetry at LHC PBAR-11, Matsue, Dezső Horváth KFKI Research Institute for Particle and Nuclear Physics, Budapest and Institute of Nuclear Research, Debrecen, Hungary

2 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 2/40 Supersymmetry (SUSY). Outline Benchmark points of CMS : cmssm excluded. New search strategy: simplified models. Results of Literature: S.P. Martin: A Supersymmetry Primer, hep-ph/ , Version 6, September 2011 D.S.M. Alves et al., The LHC New Physics Working Group: Simplified Models for LHC New Physics Searches, arxiv: v1 [hep-ph] 13 May 2011 With the support of OTKA Grant NK-81447

3 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 3/40 Problems of the Standard Model 1 3 independent (?) components: U(1) Y SU(2) L SU(3) C Gravitation? S = 2 graviton? Asymmetries: right left World Antiworld Artificial mass creation: Higgs-field ad hoc Many fundamental particles: = 13 bosons 3 2 ( ) = 48 fermions Charge quantization: Q e = Q p, Q d = Q e /3 Why the 3 fermion families? Originally: Who needs the muon?? Nucleon spin: how 1/2 produced?

4 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 4/40 Problems of the Standard Model 2 19 free parameters (too many??): 3 couplings: α, Θ W, Λ QCD ; 2 Higgs: M H, λ 9 fermion masses: 3 M l, 6 M q 4 parameters of the CKM matrix: Θ 1, Θ 2, Θ 3, δ QCD-vacuum: Θ M ν > 0 +3 masses, +4 mixing matrix Gravitational mass of the Universe: 4% ordinary matter (stars, gas, dust, ν) 23% invisible dark matter 73% mysterious dark energy Naturalness (hierarchy): The mass of the Higgs boson quadratically diverges due to radiative corrections. Cancelled if fermions and bosons exist in pairs.

5 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 5/40 Coupling constants (µ) α 1 Standard Model (µ) α (µ) α log 10 (µ [GeV]) α i : Local SU(i) couplings They almost meet at µ GeV Do they unite at high energy?

6 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 6/40 Supersymmetry (SUSY) Hypothesis: Fermions and bosons exist in pairs: Q F>= B>; Q B>= F> m B = m F Identical particles, just spins different Broken at low energy, no partners: much larger mass? Chiral multiplets SUSY Zoo Gauge multiplets S=1/2 S=0 S=1 S=1/2 quark: q L, q R squark: q 1, q 2 photon: γ photino (bino): γ( b) lepton: l L,l R slepton: l 1, l 2 weak W ± wino: W ± bosons Z zino: Z higgsino: Φ, Φ Higgs: Φ,Φ gluon: g gluino: g Scalar fermion: sfermion, boson s partner: bosino

7 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 7/40 SUSY, cont d. 2 Higgs doublets masses to upper and lower fermions m L = m R, but m L m R 8 Higgs fields 5 Higgs bosons: h 0,H 0,A 0,H ± Higgs-parameters: tanβ = v 1 /v 2, masses SUSY s quantum number: R parity R = ( 1) 3B L+2S R = +1 particle, R = 1 SUSY partner (sparticle) Parity-like: R 2 = +1 If R conserved, lightest sparticle (LSP) stable R parity may not be much violated: we would see Neutral LSP: excellent dark matter candidate

8 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 8/40 SUSY: coupling constants Unification OK! Bend at low energies: SUSY enters with many new particles more loop corrections

9 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 9/40 Minimal Supersymmetric SM (MSSM) Electroweak symmetry breaking MSSM-fermions mix into mass eigenstates {Electroweak gauginos + higgsinos} {charginos and neutralinos } { γ, W ±, Z; h 0, H 0, H ± } { χ ± 1, χ± 2 ; χ0 1, χ0 2, χ0 3, χ0 4 } mass grows with index Lightest SUSY particle (LSP) depends on model, e.g. msugra: χ 0 1 or GMSB: gravitino ( G) SUSY breaking many (> 100) new parameters masses, couplings, mixing angles Lots of model variants, huge parameter space, different constraints.

10 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 10/40 SM and MSSM: menagerie Almost 50 % discovered already!! We see half ( 1) of all SUSY particles

11 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 11/40 CMSSM, msugra Constrained MSSM or Minimal Supergravity Model Many simplification constraints (boundary conditions), or 6 parameters, e.g. in msugra: m 1/2 : fermion masses at the Grand Unification energy (GUE GeV) m 0 : boson masses at GUE A 0 : SUSY-breaking triple (X Y Higgs) couplings at GUE tanβ = v 1 /v 2 : vacuum exp. values upper/lower Higgs fields m A : mass of a Higgs boson µ: mixing parameter of the higgsinos (sign ±) Really sensitive parameters: m 0 and m 1/2

12 SUSY models Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 12/40

13 Many-many alternative models Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 13/40

14 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 14/40 Experimental limits, constraints No SUSY phenomenon observed, the data limit the parameter space LEP, Tevatron, LHC: Higgs sector Mass of SM Higgs from direct searches 114 < M H < 141 GeV; H h 0 Fitting electroweak data Search for neutral Higgs bosons (h and A) BR(b sγ) measurements at B-factories Anomalous magnetic moment of the muon (BNL) WMAP (Wilkinson Microwave Anisotropy Probe): density of dark matter (DM), indirect Direct searches for DM with ν-detectors

15 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 15/40 SUSY search Production in pairs, decay to other SUSY particle (if R conserved) Lightest (LSP) stable, neutral, not observable Signal: missing energy Tipical SUSY decays (LSP = χ 0 1 ): squark: q q + g; q + χ 0 1 slepton: l l + χ 0 1 gluino: g q + q + χ 0 1 ; g + χ0 1 wino: W e + ν e + χ 0 1

16 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 16/40 SUSY testing points of CMS SUSY benchmark points cmssm! Look where there is light LM: Low Mass HM: High Mass LM1 favored by WMAP LM0 added later + LM

17 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 17/40 CMS strategies for discovery α T search for early discovery in (forced) 2-jet events (E T (J 1 ) > E T (J 2 )): Cut α T = E T(J 2 ) = M T (J 1,J 2 ) E T (J 2 ) (ET (J 1 )+E T (J 2 )) 2 (p x (J 1 )+p x (J 2 )) 2 (p y (J 1 )+p y (J 2 )) 2 Exclusive 2-jet, inclusive 3-jet search Jets + H T for > 2 jets, inclusive Scalar mom. sum: H T = i p T (J i) ; Missing transverse mom.: MHT = H T = i p T (J i) Razor search: test kinematic consistency for pair production of heavy particles Two jets (inv. mass M R ) + 0 or 1 lepton

18 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 18/40 Luminosity Rate of reaction with σ cross-section: R = σl Luminosity: L = fn N 1N 2 A [L] = s 1 cm 2 ( flux) f: circulation frequency; n: nr. of bunches in ring N 1,N 2 particles/bunch; A: spatial overlap Rate of reaction with cross section σ at ǫ efficiency R = ǫσl Integrated luminosity: t 2 t 1 Ldt; [pb 1, fb 1 ]

19 LHC, p-p at 7 TeV, 2011 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 19/40

20 LHC, Pb-Pb at 7 TeV, 2011 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 20/40

21 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 21/40 LHC, p-p at 7 TeV: 2010 vs In 2010 LHC: 46.4 pb 1, CMS: 42.5 pb 1 In 2011 LHC: 5.7 fb 1, CMS: 5.2 fb 1 In 2011 luminosity per day total in 2010 Oct. 2011: bunches, 1318 collisions in CMS and ATLAS Spacing: 50 ns, collision angle: 170 µrad LHC is like Formula 1: boring without collisions

22 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 22/40 SUSY search by CMS Force 2-jets α T = E T(J 2 ) M T (J 1,J 2 ) is good against hadronic background Cut: α T > 0.55 CMS Collaboration, Phys.Lett.B698: , data, 35 pb 1

23 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 23/40 SUSY search: 2010 data, pb 1 CMS Collaboration, Phys.Lett.B698: ,2011. CMS Analysis Note SUS pas LM0 and LM1 are excluded by 2010 CMS data

24 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 24/40 LHC, 2011: cmssm excluded Same for ATLAS, of course

25 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 25/40 What and where to look for? Even if SUSY is valid, MSSM or cmssm may not be. If we find new physics, how can we tell it is SUSY? Simplified models easier interpretation LHC inverse problem: Given model and parameters prediction of reactions But experiment works the other way around: We have to tell which model from the data. SUSY: Cascade decays are model-dependent Simplified models give reactions with few particles dependence on few masses and cross sections with relatively wide allowed intervals characteristic for several models

26 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 26/40 Simplified Models Few on-shell particles, simple topology and decays Not model-independent, but possibly associated with several models. Possible new physics on well understood SM-base What can we learn of such analysis? Boundaries of search sensitivity, both for data analysis and for new theories. Characterizing new physics signals: what models can be associated? Limits on more general models: from possible cross-sections.

27 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 27/40 Topologies of simplified models Basic topologies with no lepton: gg g g 2(qq + LSP) qg q g qqq + 2 LSP) qq q q qq +2 LSP) and we can add one or more leptons.

28 Simplified models: the playground c Sue Ann Koay, HCP-2011, Paris Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 28/40

29 Simplified models: CMS searches c Sue Ann Koay, HCP-2011, Paris Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 29/40

30 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 30/40 Simplified models: example Model-independent exclusion for final states: CMS Collaboration, arxiv: v1

31 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 31/40 Simplified models: CMS exclusion c Sue Ann Koay, HCP-2011, Paris

32 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 32/40 Exclusion with simplified models Search for new physics at CMS with jets and missing momentum, CMS-PAS-SUS , Pure hadronic events: no neutrino, missing momentum from LSP g g 4 t-jets + LSPs CL 95% exclusion for production of gluino pairs to test models

33 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 33/40 Conclusion msugra does not seem to be supported by experimental data (g-2, LEP, WMAP, LHC,...) More general models needed Simplified approaches: search for non-sm phenomena in simple reactions with on-shell particles. Helps to find new, characteristic reactions. Identify new observation with possible models Adjust theory to data, not the other way around. Experimentalist: What happens to you if we exclude the whole SUSY in 2012? Theorist: We are far from that, MSSM is not the whole SUSY. And anyways, we are not doing that only...

34 Thank you for your attention Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 34/40

35 Spare slides for questions Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 35/40

36 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 36/40 MSSM mass spectrum: preconceptions Even if we remain sceptic it is worthwhile to know what do most of the model constructors think (after S.P. Martin) R parity is barely violated LSP: χ 0 1 or gravitino Gluino mass M 3 m( g) m( χ 0 1 ),m( χ0 2 ),m( χ± 1 ) m(ũ i ) m( d i ) m( c i ) m( s i ) m( l i ) m(ũ i ) m( d i ) m( c i ) m( s i ) > (0,6 MSUGRA...0,8 GMSB )m( g) m(ũ L ) m(ũ R )...m( s L ) m( s R ) and m(ẽ L ) m(ẽ R ),m( µ L ) m( µ R ) as M 2 L M2 R + 0,5m2 1/2. t 1, b 1 lightest squarks and τ 1 lightest charged slepton (mixing, Higgs coupling) m(h 0 ) 150 GeV m(a),m(h ± ),m(h 0 )

37 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 37/40 OSET: On-Shell Effective Theory CMS + theory, Off-shell particles: hard to identify, missing energy harder to determine Assume simple production and simple decay of new particle, analyze decay spectra, find corresponding deviations from SM. LHC phenomena Lagrangian of new physics Main study: gluino and sqark production and decay

38 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 38/40 OSET: On-Shell Effective Theory Pair production, 2 decay modes Amplitudes (cross-sections and branching ratios) free parameters N.Arkani-Hamed et al: MARMOSET, hep-ph/

39 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 39/40 Phenomenological MSSM Random space points in (105 ) 19-parameter pmssm (1st and 2nd generation sfermions assumed degenerate) 10 (real) sfermion masses 3 gaugino masses 3 trilinear couplings) µ, tanβ, M A. Masses: GeV TeV, 1 < tanβ < 60 Experimental and theoretical constraints applied So far (msugra, GMSB,...) overlooked phenomena could emerge C.F.Berger, J.S.Gainer, J.L.Hewett, T.G.Rizzo: Supersymmetry Without Prejudice, JHEP 0902:023,2009.

40 Horváth Dezső: SUSY Search at LHC PBAR-11, Matsue, p. 40/40 The missing MSSM menagerie Kind spin R parity gauge eigenstate mass eigenstate Higgs bosons 0 +1 H 0 1,H0 2,H+ 1,H 2 h0,h 0,A 0,H ± ũ L,ũ R, d L, d R same squark 0-1 s L, s R, c L, c R same t L, t R, b L, b R t 1, t 2, b 1, b 2 ẽ L,ẽ R, ν e same slepton 0-1 µ L, µ R, ν µ same τ L, τ R, ν τ τ 1, τ 2, ν τ neutralino 1/2-1 B 0, W 0, H 0 1, H 0 2 χ 0 1, χ0 2, χ0 3, χ0 4 chargino 1/2-1 W ±, H + 1, H 2 χ ± 1, χ± 2 gluino 1/2-1 g same goldstino 1/2-1 G same gravitino 3/2