Physics Prospects at the LHC John ELLIS CERN

Physics Prospects at the LHC John ELLIS, CERN, Geneva, Switzerland & King’s College London

Open Questions beyond the Standard Model • What is the origin of particle masses? SUSY LHC due to a Higgs boson? • Why so many types of matter particles? LHC SUSY LHC • What is the dark matter in the Universe? • Unification of fundamental forces? SUSY LHC • Quantum theory of gravity? SUSY LHC

How Heavy is the Higgs Boson? • Direct search limit from LEP: m. H > 114. 4 Ge. V • Electroweak fit sensitive to mt (Now mt = 173. 1 ± 1. 3 Ge. V) • Best-fit value for Higgs mass: m. H = 89+35– 26 Ge. V • 95% confidence-level upper limit: m. H < 158 Ge. V, or 185 Ge. V including LEP direct limit • Tevatron exclusion: m. H < 158 Ge. V or > 175 Ge. V

Higgs Search @ Tevatron excludes Higgs between 158 & 175 Ge. V

Combining the Higgs Information m. H = 121 + 17 -6 Ge. V

Another Reason to like Susy EW data suggest m. H < 150 Ge. V As predicted by supersymmetry

Prospects for Tevatron Higgs Search 10/fb per experiment by end 2011 planned 16/fb by end 2014 proposed

A la recherche du Higgs perdu … Some Sample Higgs Signals γγ γγ ZZ* -> 4 leptons ττ

Higgs Search @ 7 Te. V Expected 95 % CL excluded region is 135 Ge. V < MH < 188 Ge. V

When will the LHC discover the Higgs boson? 1 ‘year’ @ 1033 ‘month’ @ 1032 Blaising, JE et al: 2006

Loop Corrections to Higgs Mass 2 • Consider generic fermion and boson loops: • Each is quadratically divergent: Λ 4 ∫ d k/k 2 2 • Leading divergence cancelled if x 2 Supersymmetry!

Dark Matter in the Universe Astronomers say that most of the matter in the Universe is invisible Dark Matter ‘Supersymmetric’ particles ? We shall look for them with the LHC

Minimal Supersymmetric Extension of Standard Model (MSSM) • Particles + spartners • 2 Higgs doublets, coupling μ, ratio of v. e. v. ’s = tan β • Unknown supersymmetry-breaking parameters: Scalar masses m 0, gaugino masses m 1/2, trilinear soft couplings Aλ, bilinear soft coupling Bμ • Often assume universality: Single m 0, single m 1/2, single Aλ, Bμ: not string? • Called constrained* MSSM = CMSSM (* at what scale? ) • Minimal supergravity (m. SUGRA) predicts gravitino mass: m 3/2 = m 0 and relation: Bμ = A λ – m 0

Non-Universal Scalar Masses • Different sfermions with same quantum #s? e. g. , d, s squarks? disfavoured by upper limits on flavourchanging neutral interactions • Squarks with different #s, squarks and sleptons? disfavoured in various GUT models e. g. , d. R = e. L, d. L = u. R = e. R in SU(5), all in SO(10) • Non-universal susy-breaking masses for Higgses? No reason why not! NUHM

MSSM: > 100 parameters Minimal Flavour Violation: 13 parameters (+ 6 violating CP) SU(5) unification: 7 parameters NUHM 2: 6 parameters NUHM 1 = SO(10): 5 parameters CMSSM: 4 parameters m. SUGRA: 3 parameters String?

Lightest Supersymmetric Particle • Stable in many models because of conservation of R parity: R = (-1) 2 S –L + 3 B where S = spin, L = lepton #, B = baryon # • Particles have R = +1, sparticles R = -1: Sparticles produced in pairs Heavier sparticles lighter sparticles • Lightest supersymmetric particle (LSP) stable Fayet

Possible Nature of LSP • No strong or electromagnetic interactions Otherwise would bind to matter Detectable as anomalous heavy nucleus • Possible weakly-interacting scandidates Sneutrino (Excluded by LEP, direct searches) Lightest neutralino χ (partner of Z, H, γ) Gravitino (nightmare for astrophysical detection)

Constraints on Supersymmetry • Absence of sparticles at LEP, Tevatron selectron, chargino > 100 Ge. V squarks, gluino > 300 Ge. V • Indirect constraints Higgs > 114 Ge. V, b → s γ • Density of dark matter lightest sparticle χ: 0. 094 < Ωχh 2 < 0. 124 3. 3 σ effect in gμ – 2?

Quo Vadis g - 2? • Older e+e- data show discrepancy – now 3. 4 • Disagreement with decay data – Discrepancy ~ 2 • New BABAR e+e- data agree poorly with previous e+e- data – Intermediate between e+e- and decay data • Combination with previous e+edata yield discrepancy ~ 3. 1 • New KLOE data confirm previous result

Current Constraints on CMSSM Assuming the lightest sparticle is a neutralino SU(5) universality at 1017 Ge. V Excluded because stau LSP Excluded by b s gamma WMAP constraint on relic density Preferred (? ) by latest g - 2 JE +JEOlive JE+ +Mustafayev Olive + Santoso + Sandick ++Olive Spanos

Global Supersymmetric Fit • Frequentist approach • Data used: – Precision electroweak data – Higgs mass limit – cold dark matter density – B decay data (b s , Bs + -) – g - 2 (optional) • Combine likelihood functions • Analyze CMSSM, NUHM 1 (VCMSSM, m. SUGRA) O. Buchmueller, JE et al: ar. Xiv: 0808. 4128, 0907. 5568, 0912. 1036

How Soon Might the CMSSM be Detected? O. Buchmueller, JE et al: ar. Xiv: 0808. 4128

How Soon Might the NUHM 1 be Detected? O. Buchmueller, JE et al: ar. Xiv: 0808. 4128

Spectra with likely Ranges O. Buchmueller, JE et al: ar. Xiv: 0907. 5568

Sensitivities to Constraints g - 2 O. Buchmueller, JE et al: ar. Xiv: 0808. 4128 b s

What Happens if g - 2 Dropped? CMSSM NUHM 1 Solid lines: with g - 2 Dashed lines: without g - 2 Focus-point still disfavoured, e. g. , by m. W O. Buchmueller, JE et al: ar. Xiv: 0907. 5568

Likelihood Function for Higgs Mass CMSSM O. Buchmueller, JE et al: ar. Xiv: 0907. 5568 NUHM 1

Likelihood Function for Neutralino Mass CMSSM O. Buchmueller, JE et al: ar. Xiv: 0907. 5568 NUHM 1

Correlation between Gluino & Squark Masses CMSSM O. Buchmueller, JE et al: ar. Xiv: 0907. 5568 NUHM 1

Likelihood Function for Bs + CMSSM Standard Model prediction O. Buchmueller, JE et al: ar. Xiv: 0907. 5568 NUHM 1

Nov. 20 th 2009: Jubilation 31

The LHC Physics Haystack(s) Interesting cross sections Susy Higgs • Cross sections for heavy particles ~ 1 /(1 Te. V)2 • Most have small couplings ~ α 2 • Compare with total cross section ~ 1/(100 Me. V)2 • Fraction ~ 1/1, 000, 000 • Need ~ 1, 000 events for signal • Compare needle ~ 1/100, 000 m 3 • Haystack ~ 100 m 3 • Must look in ~ 100, 000 haystacks

No Higgs yet! Higgs may decay into pairs of photons … … but the Higgs mass is about a thousand times bigger!

No Supersymmetry yet! Transverse momentum balanced, so far …

The Story so far – and to come ✔ ✔ ?

Top Pair Candidate in ATLAS

Top Pair Candidate in CMS

The LHC Sensitivity Starts to Extend Beyond the Tevatron

String Effects in 2 -2 Scattering @ LHC? • World-line becomes sheet: • Modifications of scattering amplitudes: Feng, Lust, Schlotterer, Stieberger & Taylor: ar. Xiv: 1007. 5254

Variables for Selecting Supersymmetry

Supersymmetry Search in CMS

The Role of Rapidity Supersymmetry produced more centrally than dominant backgrounds Can be used to enhance signal/background ratio

‘Dalitz Plot’ for Supersymmetric Dijets CMS selection cut Bainbridge, Buchmueller, JE, Gripaios

Supersymmetry Search in ATLAS Highest discovery potential: in jets + ET, miss + 0 lepton channel pre-selection: (~70 nb-1, L 1 jet trigger) • =1, ≥ 2, ≥ 3, ≥ 4 jets with p. T>70 (30) Ge. V final selection: • ET, miss>40 Ge. V, ΔΦ(ji, ET, miss)>0. 2 • ET, miss/Meff> 0. 3 -0. 2

LHC Sensitivity @ 7 Te. V Compared with ‘most likely’ region for CMSSM O. Buchmueller, JE et al: ar. Xiv: 0808. 4128

The LHC may Detect Many Sparticles in Many Channels Altunkaynak, Holmes, Nath, Nelson & Peim: ar. Xiv: 1008. 3423

LHC Luminosity Reaches 1031/cm 2 s

Implications of LHC Search for LC In CMSSM LHC gluino mass reach Corresponding sparticle thresholds @ LC LHC will tell LC where to look ‘month’ @ 1032 ‘month’ @ 1033 1 ‘year’ @ 1034 Blaising, JE et al: 2006

Correlation between Neutralino & Stau Masses CMSSM O. Buchmueller, JE et al: ar. Xiv: 0907. 5568 NUHM 1

Elastic Scattering Cross Sections CMSSM O. Buchmueller, JE et al: ar. Xiv: 0907. 5568 NUHM 1

Xenon 100 Experiment No events in CDMS II ‘signal’ region Expect sensitivity to ~ 10 -45 cm 2 with 200 days of data Aprile et al: ar. Xiv: 1005. 0380 Similar sensitivity with 11 days of data

Conversation with Mrs Thatcher: 1982 What do you do? Think of things for the experiments to look for, and hope they find something different Then we would not learn anything! Wouldn’t it be better if they found what you predicted?