FINDING SUPERSYMMETRY AT THE LHC

Transcription

1 FINDING SUPERSYMMETRY AT THE LHC Tilman Plehn MPI München & University of Edinburgh TeV scale supersymmetry Signals at Tevatron and LHC Measurements at LHC SUSY parameters at LHC (and ILC) Tilman Plehn: Finding Supersymmetry p.

2 WHAT S WRONG WITH THE STANDARD MODEL A brief history of the field theory mess we are in Fermi 934: weak interactions [n pe ν e and µ e ν e ν µ ] divergent four fermion amplitude: A G F E 2 unitarity violation [transition probability A 2 ] effective theory for E 6 GeV Yukawa 935: massive virtual particle exchange Fermi s theory for E M four fermions unitary for large E: A g 2 E 2 /(E 2 M 2 ) unitarity violation in WW WW [A G F E 2 ] Higgs 964: spontaneous symmetry breaking unitary gauge theory with massive W, Z [W, Z discovered 983] fermion masses linked to Yukawa couplings [top quark discoverd 995] light fundamental Higgs scalar [mass unknown] Higgs couplings fixed g HXX gm X W Tilman Plehn: Finding Supersymmetry p.2

3 WHAT S WRONG WITH THE STANDARD MODEL A brief history of the field theory mess we are in Fermi 934: weak interactions [n pe ν e and µ e ν e ν µ ] divergent four fermion amplitude: A G F E 2 unitarity violation [transition probability A 2 ] effective theory for E 6 GeV Yukawa 935: massive virtual particle exchange Fermi s theory for E M four fermions unitary for large E: A g 2 E 2 /(E 2 M 2 ) unitarity violation in WW WW [A G F E 2 ] Higgs 964: spontaneous symmetry breaking unitary gauge theory with massive W, Z [W, Z discovered 983] fermion masses linked to Yukawa couplings [top quark discoverd 995] light fundamental Higgs scalar [mass unknown] Higgs couplings fixed g HXX gm X disaster strikes: scalar mass perturbatively unstable quadratic divergences δm 2 H g 2 Λ 2 [Λ loop cutoff] all orders Higgs mass driven to cutoff m H Λ new physics needed to solve hierarchy problem m Z Λ H t H W W Tilman Plehn: Finding Supersymmetry p.3

4 Starting from data... TEV SCALE SUPERSYMMETRY:...which seem to indicate a light Higgs problem of light Higgs: mass driven to cutoff of theory δm 2 H g 2 (2m 2 W + m2 Z + m2 H 4m 2 t ) Λ 2 Veltman s condition ( ) = would be fun problem preferably solved to arbitrary loop order easy solution: counter term to cancel loops artificial, unmotivated, ugly or new physics at TeV scale: supersymmetry extra dimensions little Higgs (pseudo Goldstone Higgs) Higgsless, composite Higgs YourFavoriteNewPhysics... typically either cancellation with new particles or discussing away high scale all beautiful concepts and symmetries in general problematic to realize at TeV scale [data seriously in the way] H t H W Idea of supersymmetry: cancellation of divergences through statistics factor (-) [scalars vs. SM fermions; fermions vs. SM gauge bosons; fermions vs. SM scalars] Tilman Plehn: Finding Supersymmetry p.4

5 TEV SCALE SUPERSYMMETRY: 2 SUSY idea: solve hierarchy problem by doubling spectrum stops (scalar) cancel top loop [couplings protected] gauginos (neutral or charged) cancel W, Z loop higgsinos cancel Higgs loop [mix with gauginos] postulate gluino for 2-loop, plus sleptons and squarks hierarchy problem solved rich collider and non-collider phenomenology [broken SUSY effective theory of everything] extended Poincaré algebra, supergravity,... Change in Higgs sector adjoint Higgs field not allowed in L how to give mass to t and b? two Higgs doublets SUSY Higgs sector interesting in itself I hope Dave told you? spin d.o.f. fermion f L, f R /2 + sfermion f L, f R + gluon Gµ n-2 gluino g /2 2 Majorana gauge bosons γ, Z 2+3 Higgs bosons h o, H o, A o 3 neutralinos χ o /2 4 2 Majorana i gauge bosons W ± 2 3 Higgs bosons H ± 2 charginos χ ± i /2 2 4 Dirac graviton G 2 2 gravitino G 3/2 2 hard to catch Tilman Plehn: Finding Supersymmetry p.5

6 SUSY breaking: heavy partners TEV SCALE SUPERSYMMETRY: 3 mechanism for partner masses unknown [soft breaking keeps away quadratic divergences] link to flavor physics and baryogenesis/leptogenesis unknown SUSY breaking unknown [hidden sector, assume mediation to visible sector] maximally blind mediation at high scale: msugra [not the LHC paradigm anymore!] scalars: m, fermions: m /2, tri-scalar term: A plus sign(µ) and tan β in Higgs sector [Higgs masses free: NUHM] Alternatives to msugra gauge mediation anomaly mediation gaugino mediation? [SoftSusy,...] & % %! " $# # " % %! & measure spectrum at LHC 2 " # (' " % ' ('! +* ).-, ), # " # & " Tilman Plehn: Finding Supersymmetry p.6

7 TEV SCALE SUPERSYMMETRY: 4 Instead of SUSY breaking structures in the MSSM spectrum gauginos higgsinos mixing: m χ 2 m χ + m B m Z s w c β m Z s w s β m W m Z c w c β m z c w s β m Z s w c β m Z c w c β µ m Z s w s β m Z c w s β µ or m χ m χ + C A in MSSM m W 2mW s β 2mW c β µ! off-diagonal elements the SUSY-protected Yukawas Tilman Plehn: Finding Supersymmetry p.7

8 TEV SCALE SUPERSYMMETRY: 4 Instead of SUSY breaking structures in the MSSM spectrum gauginos higgsinos mixing: m χ 2 m χ + m B m Z s w c β m Z s w s β m W m Z c w c β m z c w s β m Z s w c β m Z c w c β µ m Z s w s β m Z c w s β µ or m χ m χ + C A in MSSM m W 2mW s β 2mW c β µ! off-diagonal elements the SUSY-protected Yukawas test of SUSY at Linear Collider: m Z s w c β m Z s w c β ( + κ d )... LC M 2 [GeV] κ u κ d κ u κ d [Kilian, TP, Richardson, Schmidt] Tilman Plehn: Finding Supersymmetry p.8

9 TEV SCALE SUPERSYMMETRY: 4 Instead of SUSY breaking structures in the MSSM spectrum gauginos higgsinos mixing: m χ 2 m χ + m B m Z s w c β m Z s w s β m W m Z c w c β m z c w s β m Z s w c β m Z c w c β µ m Z s w s β m Z c w s β µ or m χ m χ + C A in MSSM m W 2mW s β 2mW c β µ! stop and sbottom mixing in MSSM m 2 Q + m2 t s2 w m 2 Z c 2β m t (A t + µ cot β) m t (A t + µ cot β) m 2 U + m2 t s2 w m2 Z c 2β! heavy gluinos, squarks through unification: m B, W, g /m /2.4,.8, 2.6 [mass and coupling unification independent] m l, q /m /2.7, 2.5 [m m /2 ] Tilman Plehn: Finding Supersymmetry p.9

10 SUPERSYMMETRY AT HADRON COLLIDERS: Conversion of beam energy into particle mass search for new particles easier if particle produced highest possible energies required clean e + e colliders: LEP: Z pole LEP2: 26 GeV for e.g. ZH ILC/CLIC:...4 TeV in future powerful hadron colliders: Tevatron: p p with 2 TeV LHC: pp with 4 TeV [gluons] [valence quarks] LHC mass reach 3 TeV [win by luminosity] New physics at hadron colliders what is a jet and what is inside? [b, τ tag] trigger: no leptons no data σ (nb) proton - (anti)proton cross sections σ tot σ b σ jet (E T jet > s/2) σ W σ Z σ jet (E T jet > GeV) σ t σ jet (E jet T > s/4) σ Higgs (M H = 5 GeV) Tevatron LHC events/sec for L = 33 cm -2 s - huge backgrounds pp b b, WZ+jets,... statistics: S/ B > 5 called discovery -6-7 σ Higgs (M H = 5 GeV). s (TeV) -6-7 Tilman Plehn: Finding Supersymmetry p.

11 SUPERSYMMETRY AT HADRON COLLIDERS: 2 Inclusive: squarks and gluinos at Tevatron squarks, gluinos strongly interacting p p q q, q g, g g [best if m( q) m( g)] cross sections large at Tevatron [and LHC] decays to jets and LSP [additional jets and leptons possible] gaugino mass unification only for efficiency we know search for inclusive jets plus LSP ) 2 Squark Mass (GeV/c DØ Run II Preliminary L=3 pb UA UA2 DØ IA LEP +2 CDF IB DØ IB DØ II no msugra solution m(q ~ )<m( χ ) χ +/- LEP2 ~ LEP2 l Gluino Mass (GeV/c ) How do we know it is SUSY? remember: gluinos Majorana fermions jet in gluino decay q or q final state leptons with both charges like sign dileptons from g g [Barnett, Gunion, Haber] g ũ χ + g ũ * χ µ + µ χ Tilman Plehn: Finding Supersymmetry p.

12 Supersymmetry at the LHC SUPERSYMMETRY AT LHC: () possible discovery signals for new physics, exclusion of parameter space (2) measurements (3) parameter studies 4 2 CMS g(3) ~ miss E T ( fb - ) L dt =,,, 3 fb - A =, tanβ= 35, µ > miss E T (3 fb - ) h(23) g(25) ~ one m /2 (GeV) 8 6 TH q(2) ~ g(5) ~ g(2) ~ miss E T ( fb - ) q(25) ~ one Ωh 2 =.4 4 Ωh 2 = q(5) ~ miss E T ( fb - ) g() ~ one one 2 q(5) ~ h() EX Ωh 2 =.5 g(5) ~ 5 q() ~ 5 2 m cosmologically plausible region Fermilab reach: < 5 GeV (GeV) DD_2 Catania 8 Tilman Plehn: Finding Supersymmetry p.2

13 SUPERSYMMETRY AT LHC: Supersymmetry at the LHC () possible discovery signals for new physics, exclusion of parameter space (2) measurements masses, cross sections, decays (3) parameter studies MSSM Lagrangean, SUSY breaking SUSY signals include [NLO: Prospino2] QCD coupling g q q, q g q, g g g jets and /E T : pp q q, g g, q g funny tops: pp t t tri-leptons: pp χ 2 χ [ χ 2 l l χ l l; χ χ l ν] χ o + 2 χ σ tot [pb]: pp g g, q q, t t, χ 2 o χ +, ν ν, χ 2o g, χ 2o q ν ν t t χ o 2 q χ o 2 g q q g g S = 4 TeV NLO LO m [GeV] Tilman Plehn: Finding Supersymmetry p.3

14 SUPERSYMMETRY AT LHC: Supersymmetry at the LHC () possible discovery signals for new physics, exclusion of parameter space (2) measurements masses, cross sections, decays (3) parameter studies MSSM Lagrangean, SUSY breaking SUSY signals include [NLO: Prospino2] QCD coupling g q q, q g q, g g g jets and /E T : pp q q, g g, q g funny tops: pp t t tri-leptons: pp χ 2 χ [ χ 2 l l χ l l; χ χ l ν] - χ o + 2 χ σ tot [pb]: pp g g, q q, t t, χ 2 o χ +, ν ν, χ o g, χ + q t t S = 2 TeV q q NLO LO -2-3 ν ν χ + q χ o g g g m [GeV] Tilman Plehn: Finding Supersymmetry p.4

15 SUPERSYMMETRY AT LHC: 2 Supersymmetry at the LHC () possible discovery signals for new physics, exclusion of parameter space (2) measurements masses, cross sections, decays (3) parameter studies MSSM Lagrangean, SUSY breaking at least % precision to be matched at LHC [theorist s nightmare, yet unsolved] Hadron collider observables with errors masses from σ tot branching fractions from σ tot σ LO [pb].5 σ NLO [pb].5 renormalization scale in α s, y b,t factorization scale in pdf s log (µ R /µ R ) log (µ F /µ F ) log (µ R /µ R ) log (µ F /µ F ) perturbative series N c α s /π % σ NLO,gb [pb] σ NLO,gg [pb] finite terms larger [LO-NLO-NNLO: DY, Higgs] NLO errors: % for SUSY pairs [Tevatron limits not possible without NLO] log (µ R /µ R ) log (µ F /µ F ) log (µ R /µ R ) log (µ F /µ F ) Tilman Plehn: Finding Supersymmetry p.5

16 SUPERSYMMETRY AT LHC: 3 Spectra from cascade decays q q µ µ decay g q q χ 2q q µ + µ q q χ [better not via Z or to τ] q ~ χ 2o cross sections some pb [more than 3 5 events] g µ ~ o χ thresholds & edges m 2 ll < (m2 χ 2 detector resolution, calibration, systematic errors, shape analysis, cross sections as input? m 2 l )(m2 l m2 χ )/m 2 l dσ/dm ll (Events/fb - /.375GeV) dσ/dm llq (Events/fb - /5GeV) 3 2 q L cascade reconstruction established 5 5 (a) m ll (GeV) (b) m llq (GeV) [Hinchliffe, Paige,...;Allanach, Parker, Webber,...] dσ/dm lq (Events/fb - /5GeV) 2 dσ/dm lq (Events/fb - /5GeV) (c) High m lq (GeV) (c2) Low m lq (GeV) dσ/dm llq (Events/fb - /5GeV) dσ/dm zq (Events/fb - /5GeV) (d) m llq (GeV) (e) m zq (GeV) Tilman Plehn: Finding Supersymmetry p.6

17 SUPERSYMMETRY AT LHC: 3 Spectra from cascade decays q q µ µ decay g q q χ 2q q µ + µ q q χ [better not via Z or to τ] q ~ χ 2o cross sections some pb [more than 3 5 events] g µ ~ o χ thresholds & edges m 2 ll < (m2 χ 2 m 2 l )(m2 l m2 χ )/m 2 l detector resolution, calibration, systematic errors, shape analysis, cross sections as input? q L cascade reconstruction established [mass difference even better] Gluino mass [Gjelsten, Miller, Osland] now four jets instead of two b L instead, all jets b-tagged most of time: cascade correct gluino mass to % - m χ l R m~ - m χ 2 m χ m χ b ~ - m m g ~ m ~ l R m χ Sparticle masses and mass differences [GeV] m~ q L m~ b - m - m χ χ m~ g m~ b - m χ m~ q L m~ g Tilman Plehn: Finding Supersymmetry p.7

18 Complex final states with Smadgraph SUPERSYMMETRY AT LHC: 4 [Cho, Hagiwara, Kanzaki, TP, Rainwater, Stelzer] Majoranas and fermion number violation in tools like Madgraph complete set of Feynman rules [4+ processes compared: Madgraph - Whizard - Sherpa] Squarks and gluinos always with many jets cascade studies sensitive to jets? [TP, Rainwater, Skands] matrix element g g+2j and ũ L g+2j [p T,j > GeV] Pythia shower tuned at Tevatron SUSY easier than tops? σ [pb] t t 6 g g ũ L g σ j σ j σ 2j dσ/dp T [pb/gev] - -2 LHC: Susy-MadGraph Pythia: p T 2 (power) p T 2 (wimpy) Q 2 (power) Q 2 (wimpy) Q 2 (tune A) p T,j (pp tt j) p T,j 5 GeV η j <5, R jj >.4 K Pythia =.8 max p T,j (pp tt jj) p T,j 5 GeV min p T,j (pp tt jj) p T,j 5 GeV dσ/dp T [pb/gev] LHC: spsa mod Susy-MadGraph Pythia: p T 2 (power) p T 2 (wimpy) Q 2 (power) Q 2 (wimpy) Q 2 (tune A) p T,j (pp ũ L ũ L j) p T,j 5 GeV η j <5, R jj >.4 K Pythia =.25 max p T,j (pp ũ L ũ L jj) p T,j GeV min p T,j (pp ũ L ũ L jj) p T,j GeV GeV Tilman Plehn: Finding Supersymmetry p.8

19 SUPERSYMMETRY AT LHC: 5 q µ How to make sure it is SUSY µ assume squark is found in cascades q ~ o χ 2 µ ~ χ o strongly interacting scalar? [first stop towards neutralino ] straw-man model where squark is a fermion: universal extra dimensions [Cheng, Dobrescu,...; mass spectra degenerate ignore this information; cross section factor larger ignore this as well] Squark slepton cascade [Smillie, Webber] decay chain χ 2 l l l l χ compare with first KK Z and l typically largest pp q g [ q : q : 2] trick: mass variables, normalized angles [Barr] bm = m jl /m max jl most promising A = [σ(jl + ) σ(jl )]/[σ(jl + ) + σ(jl )] more than proof of feasibility [dashed SUSY] Tilman Plehn: Finding Supersymmetry p.9

20 SUPERSYMMETRY AT LHC: 6 q q µ µ Show it is SUSY QCD given like sign dileptons, gluino would be better g q ~ χ 2o µ ~ χ o if fermion, then definitely Majorana [call it gluino] compare with our straw man Gluino bottom cascade [Alves, Eboli, TP] decay chain as for gluino mass measurement compare with first KK g, q, Z, and l replace initial state asymmetry by b vs. b bm = m bl /m max bl A = [σ(bl + ) σ(bl )]/[σ(bl + ) + σ(bl )] very preliminary gluino spin accessible at LHC A ± = (σ(be + )-σ(be - ))/sum dσ/dm inv dσ/dm inv e ~ +µ ~ e ~ +µ ~ +τ ~ τ ~ UED SUSY m inv [GeV] UED bl + bl - bl + bl - m inv [GeV] m inv [GeV] Tilman Plehn: Finding Supersymmetry p.2

21 SUSY parameters from observables SUPERSYMMETRIC PARAMETERS parameters: weak-scale MSSM Lagrangean measurements: masses or edges branching fractions cross sections [Lafaye, TP, Zerwas; Fittino; Arkani-Hamed,...] errors: general correlation, statistics & systematics & theory problem in grid: huge phase space, local minimum? problem in fit: domain walls, starting values, global minimum? First go at problem ask a friend who knows how SUSY is broken msugra fit m, m /2, A, tan β, sign(µ) no problem, include indirect constraints likelihood map today [Allanach, Lester] m (TeV) M /2 (TeV) L/L(max) Tilman Plehn: Finding Supersymmetry p.2

22 SUPERSYMMETRIC PARAMETERS SUSY parameters from observables [Lafaye, TP, Zerwas; Fittino; Arkani-Hamed,...] parameters: weak-scale MSSM Lagrangean measurements: masses or edges branching fractions cross sections errors: general correlation, statistics & systematics & theory problem in grid: huge phase space, local minimum? problem in fit: domain walls, starting values, global minimum? First go at problem [TP, Lafaye, Zerwas] ask a friend who knows how SUSY is broken msugra fit m, m /2, A, tan β, sign(µ) LHC edges or masses? edges much more powerful SPSa LHC LHC ILC LHC+ILC masses edges m m / tan β A Tilman Plehn: Finding Supersymmetry p.22

23 SUPERSYMMETRIC PARAMETERS SUSY parameters from observables [Lafaye, TP, Zerwas; Fittino; Arkani-Hamed,...] parameters: weak-scale MSSM Lagrangean measurements: masses or edges branching fractions cross sections errors: general correlation, statistics & systematics & theory problem in grid: huge phase space, local minimum? problem in fit: domain walls, starting values, global minimum Combination of methods [TP, Lafaye, Zerwas] () grid for closed subset (2) fit of remaining parameters (3) complete fit more modern alternaives: simulated annealing Markov Chains LHC+ILC with no assumptions LHC ILC LHC+ILC SPSa tanβ.22±9..26±.3.6±.2 M 2.45± ±. 2.23±. 2.2 M ±5 fix ± M τ L fix ± ± M τ R 29.3± ± ± M µ L 98.7± ± ± M q3 L 498.3± 497.6± ± M t R fix 5 42± ± M b R ±3 fix ± Aτ fix -22.4± ± A t -57.8±9-5.95± ± A b ±3563 fix -977± Tilman Plehn: Finding Supersymmetry p.23

24 OUTLOOK LHC phenomenology beyond the Standard Model Tevatron perfect training ground for SUSY at LHC many new ideas: QCD matching, parameter extraction, spin measurement,... many new tools: Prospino2, Smadgraph, Sfitter,... lots of more work to be done experiment and theory have to work together LHC will be the coolest experiment ever! Tilman Plehn: Finding Supersymmetry p.24

25 Complex final states SUPERSYMMETRY AT LHC: 4 [Cho, Hagiwara, Kanzaki, TP, Rainwater, Stelzer] Majoranas and fermion number violation in tools like Madgraph complete set of Feynman rules [4+ processes compared: Madgraph - Whizard - Sherpa] Squarks and gluinos always with many jets cascade studies sensitive to jets? [TP, Rainwater, Skands] matrix element g g+2j and ũ L g+2j [p T,j > GeV] Pythia shower tuned at Tevatron SUSY easier then tops σ [pb] t t 6 g g ũ L g σ j σ j σ 2j dσ/dp T [pb/gev] dσ/dp T [pb/gev] LHC: spsa Susy-MadGraph Pythia: p T 2 (power) p T 2 (wimpy) Q 2 (power) Q 2 (wimpy) Q 2 (tune A) LHC: spsa mod Susy-MadGraph Pythia: p T 2 (power) p T 2 (wimpy) Q 2 (power) Q 2 (wimpy) Q 2 (tune A) p T,j (pp g g j) p T,j 5 GeV η j <5, R jj >.4 K Pythia =.75 p T,j (pp ũ L ũ L j) p T,j 5 GeV η j <5, R jj >.4 K Pythia =.25 max p T,j (pp g g jj) p T,j GeV max p T,j (pp ũ L ũ L jj) p T,j GeV min p T,j (pp g g jj) p T,j GeV min p T,j (pp ũ L ũ L jj) p T,j GeV GeV Tilman Plehn: Finding Supersymmetry p.25