Testing the Standard Model and Search for New Physics with CMS at LHC

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1 Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 1 Testing the Standard Model and Search for New Physics with CMS at LHC FFK-2017: International Conference on Precision Physics and Fundamental Physical Constants Dezső Horváth on behalf of the CMS Collaboration horvath.dezso@wigner.mta.hu Wigner Research Centre for Physics, Institute for Particle and Nuclear Physics, Budapest, Hungary & ATOMKI, Debrecen, Hungary

2 Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 2 Outline Glory road of the Standard Model......and its deficiencies Solution: extensions? LHC and CMS Direct tests of the Standard Model Search for supersymmetry and exotica The photon bump at 750 GeV/c 2 Plans and hopes With the support of Hungarian NKFIH Grants K and K

3 Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 3 The Zoo of the Standard Model 3 fermion families: 1 pair of quarks and 1 pair of leptons in each 3 kinds of gauge bosons: the force carriers + the Higgs boson All identified and studied! Color: the charge of the strong interaction colored quarks colorless composite hadrons of 2 kinds hadrons = mesons (qq) + baryons (qqq)

4 Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 4 Glory Road of the Standard Model Status in 2016 Includes hundreds of measurements of all experiments Expt theory expt. uncertainty Slightly deviating quantity used to change Now it is forward-backward asymmetry of e + e Z b b LEP Electroweak Working Group: Measurement Fit O meas O fit /σ meas α (5) had (m Z ) ± m Z [GeV] ± Γ Z [GeV] ± σ 0 had [nb] ± R l ± A 0,l fb ± A l (P τ ) ± R b ± R c ± A 0,b fb ± A 0,c fb ± A b ± A c ± A l (SLD) ± sin 2 θ lept eff (Q fb ) ± m W [GeV] ± Γ W [GeV] ± m t [GeV] ± March

5 LHC and its main experiments Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 5

6 Dipole magnets of LHC in the tunnel Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 6

7 Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 7 CMS: Compact Muon Solenoid ton digital camera: 100 M pixel, 40 M pictures/sec, 1000 GB/sec data Process 1000 pictures/sec intelligent filter!!

8 Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 8 The CMS Collaboration (2016) 5250 participants from 198 institutions of 45 countries 995 engineers, 279 technicians 1963 physicists with PhD (326 women, 1637 men) 922 doctoral students (202 women, 720 men) 994 MSc students (241 women, 753 men) Participants by countries of institutes (in 2012): USA: 1149, Italy: 439, Germany: 298, Russia: 234 Data: 64 petabytes, 430 publication CMS detector: huge joint effort 3000 people worked on it for 20 years!

9 A CMS event: H γγ candidate Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 9

10 CMS, 2016: H 4leptons Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 10

11 Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 11 CMS, 2016: α s (M Z ) vs. SM prediction Strong coupling constant at E = M Z

12 CMS, 2016: α s running with energy Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 12

13 Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 13 Problems of the Standard Model 1 Gravity? S = 2 graviton? Asymmetries: right left World Antiworld Artificial mass creation: Higgs-field ad hoc Charge quantization: Q e = Q p, Q d = Q e /3 Why the 3 fermion families? Nucleon spin: how 1/2 produced? 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

14 Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 14 Problems of the Standard Model 2 Neutrino mysteries M ν > 0 +3 masses, +4 mixing matrix The SM does not like them... What makes them oscillate? Are they Majorana particles ν ν? Gravitational mass of the Universe: 4% ordinary matter (stars, gas, dust, ν) 23% invisible dark matter (out of SM!) 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.

15 Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 15 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, partners: much larger mass? SUSY should solve many problems

16 Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 16 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 (B: Baryon ch., L: Lepton ch., S: Spin) 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

17 Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 17 SUSY: coupling constants Minimal Supersymmetric Standard Model: Unification! Bend at low energies: SUSY enters with many new particles more loop corrections

18 Many-many alternative models Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 18

19 Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 19 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

20 Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 20 Topologies of simplified models Basic topologies with no lepton and missing energy (signal of Lightest SUSY Particle, LSP): gg g g 2(qq + LSP) qg q g qqq + 2 LSP) and we can add one or more leptons. Negative search results confirm the SM qq q q qq +2 LSP)

21 Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 21 Many SUSY analyses just exclusion CMS, March 2017: searches for scalar top quarks Exclused regions in the LSP (χ 0 1 ) mass vs. scalar top quark (left) and gluino (right) masses at 95% confidence level using different simplified topologies, search methods and SUSY models

22 Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 22 CMS SUSY summary plot Simplified Model Spectrum (SMS) topologies

23 CMS: search for exotica Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 23

24 Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 24 The 750 GeV/c 2 excess in 2015 CMS: Barrel-barrel and barrel-endcap

25 CMS event: M γγ = 745 GeV Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 25

26 Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 26 Excess at 750 GeV/c 2, December 2015 Local p-value: Probability that the observed excess is due to random background oscillation ATLAS, 13 TeV: 3.6σ, M = 750 GeV CMS, TeV: 3.0σ, M = 750 GeV

27 Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p GeV excess: strange features X(750) γγ: S X = 0 vagy S X = 2. Scalar? Decays to photons only, why not to ff and WW, ZZ? For a scalar (Higgs-like) boson WW and ZZ dominate. Fifth interaction governs its decay? It does not fit in the standard model! Plus: ATLAS sees wide peak, CMS a narrower one. ATLAS and CMS, end of 2015, Spring 2016: Let us have more data Theory: avalanche for interpretation: 2015: 150, 2016: 350 papers World press: death of the standard model? Excited waiting for new data at start of LHC in M γγ 750 GeV blinded in both experiments. Unblinding for ICHEP, Chicago (July 2016). The excess disappeared in the SM background

28 Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 28 Conclusion We have observed the Standard Model Higgs boson, and did not find any other Higgs bosons belonging to a more general model. Let us hope for some deviation from the Standard Model (although none seen yet). The simplest SUSY models do not seem to be supported by experimental data (g-2, LEP, WMAP, LHC,...) Simplified approaches: search for non-sm phenomena in simple reactions with on-shell particles. The promising 750 GeV diphoton resonance was background oscillation. We are looking for and hoping to find new physics (Dark Matter!).

29 Thank you for your attention Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 29

30 Spare slides for questions Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 30

31 Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 31 CMS: 78 identified vertices! Many p-p collisions can be in the same event (same bunch collision). Record: 78 identified vertices. This increases data taking speed and makes analysis hard.

32 Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 32 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.

33 Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 33 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 M H = 125 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) Satellite expts WMAP and Planck: density of dark matter (DM), indirect Direct searches for DM with ν-detectors and AMS2

34 Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 34 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 )

35 Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 35 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.

36 Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 36 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

37 Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 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

38 Dezső Horváth: Search for New Physics with CMS FFK2017, Warsaw, Poland p. 38 References S.P. Martin: A Supersymmetry Primer, hep-ph/ , Version 7, January 2016 ( 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 CMS Collaboration: Many papers on search for supersymmetry and new physics inhttp://inspirehep.net/: arxiv, 2016 and Public Physics Analysis Summaries.