SUPERSYMMETRY AT THE LHC

Transcription

1 SUPERSYMMETRY AT THE LHC Tilman Plehn MPI München and University of Edinburgh A few MSSM conventions SUSY-Higgs at the LHC SUSY at the Tevatron SUSY searches at the LHC SUSY measurements at the LHC (and ILC) [sorry for skipping references altogether, many reviews around] Tilman Plehn: Supersymmetry p.

2 Starting from data... TEV SCALE SUPERSYMMETRY:...which seem to indicate a light Higgs problem of light Higgs: mass driven to cutoff of theory [remember pain to get that up] 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 solution: counter term for exact cancellation 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 really beautiful concepts and symmetries in general problematic to realize at TeV scale [data seriously in the way] Idea of supersymmetry: cancellation of divergences through statistics factor (-) [scalars vs. SM fermions; fermions vs. SM gauge bosons; fermions vs. SM scalars] Tilman Plehn: Supersymmetry p.2

3 TEV SCALE SUPERSYMMETRY: 2 SUSY idea: solve hierarchy problem by just doubling particle number?! stops (scalar) cancel top loop [couplings protected] gauginos (neutral or charged) cancel W, Z loop higgsinos cancel Higgs loop [mix with neutralinos] since we are at it, let s postulate gluino for 2-loop, plus sleptons and squarks () hierarchy problem solved (2) rich collider and non-collider phenomenology guaranteed (3) Lorentz algebra properly extended Serious 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 no MSSM know-how needed 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: Supersymmetry p.3

4 SUPERSYMMETRIC HIGGS SECTOR: Required by supersymmetry: two Higgs doublet model one (complex) Higgs doublet: 4 degrees of freedom three for longitudinal W, Z, one for scalar Higgs two Higgs doublets: 8 degrees of freedom three for longitudinal W, Z, five for Higgs particles scalars h, H, pseudoscalar A, charged H ± free parameters () still only one free mass scale: m A (2) two vacuum expectation values: tan β = v t /v b 5 45 m h max scen., tanβ = 5 4 h H A All you need to know: plateau structure [FeynHiggs] plateau Higgses coupling to W, Z M Higgs [GeV] H +- heavy H, A with tan β-enhanced coupling to b, τ 2 5 light h mass limited from above m h 35 GeV FeynHiggs M A [GeV] Tilman Plehn: Supersymmetry p.4

5 SUPERSYMMETRIC HIGGS SECTOR: 2 Challenge: find one Higgs at the LHC decoupling regime m A 6 GeV h looks like SM Higgs qq qqh qqττ other end m A 2 GeV qq qqh qqττ [of corresponding mass] in between: maybe even two bumbs No-lose theorem: qq qq{h, H } qqττ tanβ LHC(4fb - ): VV H ττ LEP2: e + e Zh VV h ττ M A [GeV] Tilman Plehn: Supersymmetry p.5

6 SUPERSYMMETRIC HIGGS SECTOR: 2 Challenge: find one Higgs at the LHC decoupling regime m A 6 GeV h looks like SM Higgs qq qqh qqττ other end m A 2 GeV qq qqh qqττ [of corresponding mass] in between: maybe even two bumbs No-lose theorem: qq qq{h, H } qqττ tanβ LHC(4fb - ): VV H ττ LEP2: e + e Zh VV h ττ M A [GeV] Nightmare: confirm SUSY Higgs sector decoupling regime m A 6 GeV Yukawa coupling for H, A, H ± : m b tan β enhanced production e.g. b b H or gb th decays H ττ, µµ or H τ ν intermediate m A 2 GeV: many (light-ish) Higgses h, H, A observable top quark decays t bh +? [Tevatron?] Tilman Plehn: Supersymmetry p.6

7 Back to the MSSM: SUSY partner masses TEV SCALE SUPERSYMMETRY: 3 mechanism of mass generation unknown [soft breaking leaves quadratic divergences alone] 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 [really not the general LHC paradigm!!!] scalars: m, fermions: m /2, tri-scalar term: A plus sign(µ) and tan β in Higgs sector [Higgs masses let free: NUHM] Alternatives to msugra gauge mediation anomaly mediation gaugino mediation [SoftSusy,...] none of them convince me & % %! " $# # " % %! & " # (' " % '! (', # " # & " ) measure spectrum instead.-, +* ) Tilman Plehn: Supersymmetry p.7

8 TEV SCALE SUPERSYMMETRY: 4 Structures in the SUSY 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 ] lightest SUSY partner χ, ν after dark matter data χ B, W [gravitinos?] Tilman Plehn: Supersymmetry p.8

9 TEVATRON & LHC 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 backgrounds pp jj or pp WZ+jets statistics: S/ B > 5 we call discovery 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 Tevatron LHC σ jet (E jet T > s/4) σ Higgs (M H = 5 GeV) σ Higgs (M H = 5 GeV). s (TeV) events/sec for L = 33 cm -2 s - Tilman Plehn: Supersymmetry p.9

10 SUPERSYMMETRY AT THE TEVATRON: Inclusive: squarks and gluinos at Tevatron squarks, gluinos strongly interacting, σ pb p p q q, q g, g g [best if m( q) m( g)] decays to jets and LSP and g q q, q L q χ 2, q R q χ additional jets and leptons possible very promising search for jets plus LSP ) 2 Squark Mass (GeV/c DØ Run II Preliminary L=3 pb UA UA2 DØ IA CDF IB DØ IB DØ II χ +/- LEP2 ~ LEP2 l no msugra solution Necessary model assumptions assume % branching into inclusive jets+lsp for detector efficiencies m( χ 2 ),... gluino decay into squark or vice versa? msugra assumed, but effect moderate LEP +2 m(q ~ )<m( χ ) Gluino Mass (GeV/c ) Tilman Plehn: Supersymmetry p.

11 SUPERSYMMETRY AT THE TEVATRON: 2 More specialized: trilepton channels generally assumed that charginos are light largest cross section p p χ + χ 2 decays χ + l+ ν χ and χ 2 l + l χ gaugino rate determined by t channel squark signature plagued by W, Z background about to pass LEP2 chargino limits ) BR(3l) (pb) ± χ σ(χ LEP Chargino Searches Search for χ ± M(χ ) M(χ2 ) ± χ 2 3l+X 2M(χ ); M(slepton) > M(χ2 ) tanβ = 3, µ >, no slepton mixing heavy-squarks 3l-max large-m - DØ, 32 pb Preliminary Expected Limit (no τ) Observed Limit Expected Limit Chargino Mass (GeV) Tilman Plehn: Supersymmetry p.

12 SUPERSYMMETRY AT THE TEVATRON: 2 More specialized: trilepton channels generally assumed that charginos are light largest cross section p p χ + χ 2 decays χ + l+ ν χ and χ 2 l + l χ gaugino rate determined by t channel squark signature plagued by W, Z background about to pass LEP2 chargino limits ) BR(3l) (pb) ± χ σ(χ LEP Chargino Searches Search for χ ± M(χ ) M(χ2 ) ± χ 2 3l+X 2M(χ ); M(slepton) > M(χ2 ) tanβ = 3, µ >, no slepton mixing heavy-squarks 3l-max large-m - DØ, 32 pb Preliminary Expected Limit (no τ) Observed Limit Expected Limit Chargino Mass (GeV) Even more specialized: long-lived gauginos stable on the detector time scale of ns like massive muons in tracker muon chamber gauginos motivated by GMSB or AMSB SUSY at the LHC does not come out of nowhere! ) (pb) χ σ (p p χ LEP Excluded D Run II Preliminary - L = 39 pb 95% CL Cross Section Limit NLO Cross Section Prediction Gaugino-like Chargino Mass (GeV) Tilman Plehn: 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 included [NLO: Prospino2] 3 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 like sign dileptons: pp g g [ g ũū χ + dū or g ũ u χ du] tri-leptons: pp χ 2 χ 2 - [ χ 2 l l χ l l; χ χ l ν] -2 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: 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 included [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 like sign dileptons: pp g g [ g ũū χ + dū or g ũ u χ du] tri-leptons: pp χ 2 χ - -2 [ χ 2 l l χ l l; χ χ l ν] -3 ν 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 χ + q t t χ o g g g S = 2 TeV q q NLO LO m [GeV] Tilman Plehn: Supersymmetry p.4

15 SUPERSYMMETRY AT LHC: 2 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 great 5 5 (a) m ll (GeV) (b) m llq (GeV) [known even from Atlas TDR] 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: Supersymmetry p.5

16 SUPERSYMMETRY AT LHC: 2 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 great [know now: mass differences even better] Example: gluino mass now four jets instead of two b L instead, all jets b-tagged most of time: cascade identified gluino mass to % [statistical error dominant] - 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: Supersymmetry p.6

17 Complex final states SUPERSYMMETRY AT LHC: 3 [e.g. SUSY-Madevent] Majoranas and fermion number violation in tools like Madgraph complete set of Feynman rules [4+ processes compared with Whizard and Sherpa] Squarks and gluinos always with many jets cascade studies sensitive to jets? matrix element g g+2j and ũ L g+2j [p T,j > GeV] Phythia 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: Supersymmetry p.7

18 Complex final states SUPERSYMMETRY AT LHC: 3 [e.g. SUSY-Madevent] Majoranas and fermion number violation in tools like Madgraph complete set of Feynman rules [4+ processes compared with Whizard and Sherpa] Squarks and gluinos always with many jets cascade studies sensitive to jets? matrix element g g+2j and ũ L g+2j [p T,j > GeV] Phythia 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: Supersymmetry p.8

19 SUPERSYMMETRY AT LHC: 4 How to make sure it is SUSY assume neutralino is found in cascades compare with a model where gluino is a boson,... q µ µ straw man: universal extra dimensions q ~ χ 2o [mass spectra degenerate ignore this information; cross section factor larger ignore this as well] µ ~ o χ Slepton cascade decay chain χ 2 l l l l χ compare with first excited Z and l initial-state asymmetry pp q g [ q/ q 2] bm = m jl /m max jl most promising A = [σ(jl + ) σ(jl )]/[σ(jl + ) + σ(jl )] assume hierarchical SPSa spectrum [dashed SUSY, solid UED] we can tell spin in cascade Tilman Plehn: Supersymmetry p.9

20 SUPERSYMMETRY AT LHC: 4 How to make sure it is SUSY assume neutralino is found in cascades compare with a model where gluino is a boson,... q µ µ straw man: universal extra dimensions q ~ χ 2o [mass spectra degenerate ignore this information; cross section factor larger ignore this as well] µ ~ o χ Slepton cascade decay chain χ 2 l l l l χ compare with first excited Z and l initial-state asymmetry pp q g [ q/ q 2] bm = m jl /m max jl most promising A = [σ(jl + ) σ(jl )]/[σ(jl + ) + σ(jl )] assume non-hierarchical UED spectrum [dashed SUSY, solid UED] we can tell spin in cascade Tilman Plehn: Supersymmetry p.2

21 SUSY parameters from observables SUPERSYMMETRIC PARAMETERS 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 ask a friend who knows how SUSY is broken msugra fit m, m /2, A, tan β, sign(mu) no problem, include indirect constraints who the hell believes in msugra? msugra just testing ground for methods m (TeV) M /2 (TeV) L/L(max) Tilman Plehn: Supersymmetry p.2

22 SUPERSYMMETRIC PARAMETERS SUSY parameters from observables 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 ask a friend who knows how SUSY is broken 8 msugra fit m, m /2, A, tan β, sign(mu) χ 2 (today) 6 4 CMSSM, µ > tanβ =, A = no problem, include indirect constraints who the hell believes in msugra? 2 tanβ =, A = +m /2 tanβ =, A = -m /2 tanβ =, A = +2 m /2 tanβ =, A = -2 m / msugra just testing ground for methods m /2 [GeV] Tilman Plehn: Supersymmetry p.22

23 SUPERSYMMETRIC PARAMETERS SUSY parameters from observables 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 [Sfitter, Fittino] () 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: Supersymmetry p.23

24 OUTLOOK LHC phenomenology beyond the Standard Model world-wide pheno-experimental effort rolling many new tools/ideas on the market, waiting to be tested lots of more work to be done by now fast-growing and exciting field We will be able to do amazing things at the LHC! Tilman Plehn: Supersymmetry p.24

25 B PHYSICS AND SUPERSYMMETRY W + b s Search channel: B s µµ s-channel exchanges dominant: H, Z, γ suppressed in Standard Model [BR SM (2.4 ±.5) 9 ] more Higgs bosons in 2HDM tan β enhancement of s channel Higgses [BR 2HDM tan 6 β/m 4 A ] additional Higgs loop charginos in MSSM tan β enhancement for Higgsinos gluino loop for non-minimal flavor physics... b b t H + t χ + t s s Bottom Yukawa in the MSSM gluino-sbottom loops universal: y b y b /( + b ) b b g large, leading in tan β & resummable b α s tan β m g µ/max 2 (m b, g ) decoupling in MSSM, but not in MSSM+µ [similar terms for chargino/neutralino exchange] easy to implement in MC, numerically great for tan β > enhancement good for SUSY signals, but pain in analyses Tilman Plehn: Supersymmetry p.25