Szuperszimmetria keresése az LHC-nál

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1 Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 1/37 Szuperszimmetria keresése az LHC-nál ATOMKI-szeminárium, Debrecen, Horváth Dezső MTA KFKI RMKI, Budapest és MTA ATOMKI, Debrecen

2 Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 2/37 Outline Supersymmetry (SUSY). SUSY models: msugra, cmssm, GMSB,... Benchmark points of CMS. Exclusion in the SUSY parameter space. Simplified models. New search strategy? iterature: S.P. Martin: A Supersymmetry Primer, hep-ph/ , Version 5, 2008 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 The LHC New Physics Working Group: Signatures of New Physics at the LHC, With the support of OTKA Grant NK-81447

3 Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 3/37 roblems 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: Szuperszimmetria keresése Debrecen, fólia p. 4/37 roblems 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 +7 parameters 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: Szuperszimmetria keresése Debrecen, fólia p. 5/37 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: Szuperszimmetria keresése Debrecen, fólia p. 6/37 Supersymmetry (SUSY) Fermions and bosons 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: Szuperszimmetria keresése Debrecen, fólia p. 7/37 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 can be dark matter (ρ 0,1 GeV/cm 3!!)

8 Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 8/37 SUSY: coupling constants Unification! Bend at low energies: SUSY enters with many new particles more loop corrections

9 Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 9/37 inimal 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: Szuperszimmetria keresése Debrecen, fólia p. 10/37 SM and MSSM: menagerie Almost 50 % discovered already!! (We see half ( 1) of all SUSY particles :-)

11 Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 11/37 CMSSM, msugra nstrained MSSM or Minimal Supergravity Model any simplification constraints (boundary conditions), 05 5 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 ±)

12 SUSY models Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 12/37

13 Many-many alternative models Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 13/37

14 Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 14/37 Experimental limits, constraints No SUSY phenomenon observed, the data limit the parameter space LEP measurements: Higgs sector Mass of SM Higgs from direct searches M H > 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: Szuperszimmetria keresése Debrecen, fólia p. 15/37 SSM mass spectrum: preconceptions ven 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 )

16 Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 16/37 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

17 Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 17/37 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

18 Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 18/37 SUSY search at LHC Look for excess above SM expectation: multi-jet events with high E miss T. If found, study it, how real. If real, make a prearranged SUSY selection. Look for specific features (e.g. long-lived sleptons). Look for b-jets, lepton pairs, τ s. Determine SUSY parameters with global fitting, search for cut-off.

19 Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 19/37 SUSY testing points of CMS USY benchmark points MSUGRA! Look where there is light LM: Low Mass M: High Mass Favorit: LM1 M0 added later + LM

20 Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 20/37 SUGRA: test points and constraints Blue band is allowed by WMAP LM1 left, LM0 added later...

21 Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 21/37 Stop search in LM1 Stop final state: b-jet + l ± + E miss Stop signal: M inv (l ± b) cutoff at E miss < 180 GeV Identification: t 3 hadron jets b-tag, M(W), M(t)

22 Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 22/37 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

23 Luminosity CM energy in fixed target (X X collision) ECM 2 = s (p 1 + p 2 ) 2 = 2M X E b + 2MX 2 E CM E b Colliding beams with E b energy: ECM 2 = s 4E2 b E CM 2E b 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 ] Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 23/37

24 Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 24/37 LHC, 7 TeV: 2010 data set vs In 2010 HC: 46.4 pb 1, CMS: 42.5 pb 1 14 March - 14 May 2011 LHC: 1.0 fb 1, CMS: 0.92 fb 1 In June 2011 luminosity per day total in June 2011: bunches, 1042 collisions in CMS and ATLAS Spacing: 50 ns, collision angle: 170 µrad LHC is like Formula 1: boring without collisions

25 Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 25/37 SUSY search by CMS T is good against hadronic background Cut: α T > 0.55 CMS Collaboration, Phys.Lett.B698: , data, 35 pb 1

26 Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 26/37 USY 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

27 Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 27/37 SUSY search: two more analyses Analysis Note SUS pas es and CL s = CL s+b /CL b CMS Analysis Note SUS pas Two jets (of inv. mass M R )

28 Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 28/37 SUSY search: a new α T analysis tanβ = α T > 0.55 CMS Analysis Note SUS pas: Further interpretation of the search for supersymmetry based on α T

29 Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 29/37 ATLAS, all-hadronic, 2010 data More agressive search, not too sensitive to tanβ and A 0 Search for squarks and gluinos using final states with jets and missing transverse momentum with the ATLAS detector in sqrt(s) = 7 TeV proton-proton collisions. ATLAS, arxiv , Feb. 2011

30 Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 30/37 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 latively wide allowed intervals characteristic for several models

31 Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 31/37 OSET: On-Shell Effective Theory CMS + theory, ff-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

32 Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 32/37 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/

33 Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 33/37 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.

34 Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 34/37 LHC New Physics Working Group Theorists helping ATLAS and CMS to find benchmark points to check Example: m( g) < m( q i ), LSP = χ 0 direct decay, g qq χ 0 1-step cascade (W), g qq χ ± qq W ± χ 0 1-step cascade (Z), g qq χ 0 qq Z 0 χ 0 Z better than W, does not decay to neutrínos. Hadronic decay dominates in W and Z, no lepton, missing transverse energy is for LSP Signature: 4 jets + large missing energy

35 Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 35/37 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 o 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.

36 Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 36/37 Exclusion with simplified models Search for new physics at CMS with jets and missing momentum, CMS PAS SUS , April 2011 Pure hadronic events: no neutrino, missing momentum from LSP g g 4 jets + LSPs q q 2 jets + LSPs 95 % exclusion curves for production of gluino and squark pairs Maximal cross-sections eliminate models Selection: maximal missing transverse momentum

37 Horváth Dezső: Szuperszimmetria keresése Debrecen, fólia p. 37/37 Conclusion SUGRA does not seem to be supported by experimental data (g-2, LEP, WMAP, LHC,...) More general models needed Simplified approaches: OSET, pmssm, simple reactions. Helps to find new, characteristic reactions. Adjust theory to data, not the other way around.