Implications of first LHC results

Transcription

1 Implications of first LHC results 1) Large extra dimensions ( 2) SuperSymmetry ( Alessandro Strumia with R. Franceschini, G. Giudice, P. Paolo Giardino, P. Lodone

2 The main goal of LHC is understanding why the weak scale is small. Maybe the hierarchy problem was a good guideline. Maybe we lost 30 years. A new symmetry Scalar H H + θ Keeps H massless. Goldstone boson. Vector A µ A µ + µ θ Keeps A µ massless In 5 dims: H = A 5 Higgs has weak-scale size Fermion Ψ e iθγ 5Ψ Keeps Ψ massless. H SUSY Ψ. Technicolour H bound state like π Large extra dims H is a string or... Warped extra dims Dual to technicolor

3 Large extra dimensions

4 Collider signals (1) Graviton emission (2) Tree-level graviton exchange (3) Graviton loop (4) Trans-Planckian

5 No black holes in first LHC data

6 / d! ev ) dn ev (1/N " First LHC data: pp jj Ldt = 3.1pb ATLAS at 3.1/pb -1 # = 3 TeV (+0.09), s=7 TeV < m jj <520 GeV 520< m jj <800 GeV (+0.03) 800< m jj <1200 GeV (+0.06) >1200 GeV (+0.09) m jj QCD Prediction Theoretical Uncertainties Total Systematics ATLAS! y -y 1 2 = e FIG. 1. The normalized χ distributions for 340 < m jj < 520 GeV, 520 <m jj < 800 GeV, 800 <m jj < 1200 GeV, and m jj > 1200 GeV, with plotting offsets shown in parentheses. 6 CMS at 36/pb Use dijet c.o.m. scattering angle, d" dijet /d! 1/" dijet dijet R C January 24, 2011 Dijet Angular Distri data 2.5 CMS Preliminary CMS QCD prediction s = 7 TeV Theory uncertainty -1 L = 36 pb # = 5 TeV ATLAS " M jj > 2.2 TeV (+0.5) Ldt=3.1 pb 1.8 < M < 2.2 TeV (+0.4) QCD jj Prediction Theoretical Uncertainties Total Systematics # = 2.0 TeV Data < M jj < 1.8 TeV (+0.3) 1.1 < M jj < 1.4 TeV (+0.25) 0.85 < M jj < 1.1 TeV (+0.2) 0.65 < M jj < 0.85 TeV (+0.15) 0.5 < M jj < 0.65 TeV (+0.1) 0.35 < M jj < 0.5 TeV (+0.05), s=7 TeV 1/N dn/d! dijet < M < 0.35 TeV jj dijet Figure 1: The measured dijet angular distributions, corrected to the particle level, for several regions Monday, in M jj. The January distributions 24, are 2011 offset from zero by the amount indicated by the parentheses next to the M jj labels. The data points include statistical and systematic uncertainties. The results are compared to the predictions of pqcd at NLO without new physics (solid line) and with a contact interaction term of compositeness scale Λ = 5 TeV (dashed line). The shaded band shows the theoretical uncertainties that include scale variations, PDF uncertainties, and non-perturbative correction uncertainties. FIG. 2. Dijet centrality ratio, R C,asafun all events above a mass of 1400 GeV plott Shown are the QCD prediction with system! Com appro angu! use but c Figure 6: χ d Λ = 3 TeV. N Greg Landsberg, Quest for Ne χ = angular jj distance. Coulomb-like QCD gives a quasi-flat distribution. New massive particles or effective O give effects at large M jj and small angle χ

7 Loop level graviton exchange At low energy is described by the dimension 6 effective operator L = c Υ Υ, Υ = 1 2 ( f fγ µ γ 5 f) 2 95% CL limits on c Υ /4π 1/2 in TeV Experiment Process + LEP combined e + e l + l LEP combined e + e b b ZEUS, H1 e + p and e p DØ p p e + e CDF p p l + l CCFR νn scattering DØ p p jj ATLAS at 7 TeV with 3.1/pb pp jj CMS at 7 TeV with 36/pb pp jj combined LHC improves on TeVatron but not on LEP

8 Tree level graviton exchange At low energy is described by the dimension 8 effective operator L eff = c T T T = 1 2( Tµν T µν irrelevant {}}{ T µ µ T ν ν δ + 2 ) 2 ( Ψ Ψ + ΨAΨ + F 2 µν) 2 Independently produced by brane fluctuations at loop level. High dimensionality: energy is the key factor and early LHC wins Coefficient: parameterize as c T = 8/MT 4 (Hewett normalization). Signals: pp jj is considered dirty by actually is much better at low statistics: σ = ( 2 TeV M T ) pb for pp jj 10.4 fb for pp µ + µ 21.3 fb for pp γγ thanks to the energetic uu uu. (cuts: s = 7 TeV, M eff > 1 TeV, η < 2.5)

9 Bounds on M T Experiment Process + LEP e + e γγ 0.93 TeV 1.01 TeV LEP e + e e + e 1.18 TeV 1.17 TeV H1, ZEUS e + p and e p 0.74 TeV 0.73 TeV CDF p p e + e, γγ 0.99 TeV 0.96 TeV DØ p p e + e, γγ 1.28 TeV 1.14 TeV DØ p p jj 1.48 TeV 1.48 TeV CMS at 7 TeV with 34/pb pp γγ 1.72 TeV 1.70 TeV ATLAS at 7 TeV with 3.1/pb pp jj 2.2 TeV 2.1 TeV CMS at 7 TeV with 36/pb pp jj 4.2 TeV 3.4 TeV 10 Bounds on graviton exchange at tree level in 1 TeV 4 5 coefficent c T ±8 M T H1,ZEUS ep LEP e e ΓΓ LEP e e e e D0, CDF pp e e,γγ D0 pp jj CMS pp ΓΓ with ATLAS pp jj with CMS pp jj

10 The LHC data M T 2.5 TeV, M T 2.5 TeV, M T 2 TeV, M T 2 TeV, SM dn dχ N dn dχ N M T 3.5 TeV, M T 3.5 TeV, M T 3 TeV, M T 3 TeV, SM Χ Χ Computed implementing in MadGraph and Pythia

11 Fitting the full amplitude A = S(s)T 2 µν Truncate KK tower at m < Λ to avoid UV divergence: S(s) = 1 M 2 Pl c T = S(s Λ 2 ) = i 1 s m 2 i + im iγ G (m i ) = 1 M 2+δ π δ/2 Λ δ 2 D q <Λ d δ q s q 2 + iε (1 δ/2)γ(δ/2) MD δ+2 8 MT 4 for δ > 2 π MD 4 ln s Λ 2 for δ = 2 iπ for δ = 1 s M 3 D Subtelty: S = S i.e. it is ok to KK q Γ G = m 3 πm 2 Pl and ignore the graviton width

12 S 2 vs S 2 : subtleties under the carpet Including Γ G : S 2 = (Re S) 2 + (Im S) 2 /ɛ with ɛ = πγ G /2 m (s/m 2 D )1+δ/2. Consider just one particle with coupling g (g E/M Pl 1 for KK gravitons): σ = One would guess σ g 4 but actually σ g 2, due to pp graviton. Next graviton decays with 100% probability and width Γ mg 2. For flat extra dimensions Γ is small: gravitons decay far away from the detector. Resonant graviton production must be subtracted We find σ subtracted g 4, up to O(g 4 ) terms, such as NLO corrections to Γ. We presume that S 2 subtracted = S 2 is the right result Anyhow, even the unsubtracted 1/g 2 enhancement (present for δ = 1) is numerically irrelevant for pp jj. 2

13 Bound on the full amplitude (M D, Λ) coupling M D coupling M D D D Shaded: LHC (continuous = CMS; dashed = ALTAS; dotted ATLAS F χ ) Blue: gravition emission, ignoring the dependence on Λ Red: NDA estimate of graviton loop Gray: non-perturbative quantum gravity

14 SUSY

15 First SUSY Result at the LHC! Search for high mass squark & gluino production in events with large missing transverse energy and two or more jets xpanded the excluded range established during the last 20 years (!) by ~factor of two with only 35 pb -1! LHC End-Of-Year Jamboree December 17 th 2010 $= $A&B(/$A1=1C$DE:,(-$!"# L$#%& '( )*$#+,- (.! (/ 0 /10 /12 (1/ (1. 2 /12 (1/ (1. (13 4 /14 (1( (15 (16! "#"$!" %#13$ & 3"45 Philipp Schieferdecker (KIT) First LHC data!"!#$%&'()'*+,!"#$%&$'()&#*$+,(-$./&01*(*$2 L345' 6+ $"#*$789:,(-20 &/ $ L3+5' 6+ $"#*$78;<,(- = >?>@ $3$DE:,(-$ gluino mass M 3 in GeV outside CMSSM within CMSSM excluded Actually a bound on m q and M 3, up to 700 GeV in the CMSSM In the following we ignore g µ 2 or Ω DM ; they point to heavier m SUSY.

16 The little hierarchy problem Fix tan β = 3 and A 0 = 0; the overall SUSY mass scale is fixed by tree level m 2 h MZ 2 0.2m M 3 2 2µ2 = (91 GeV) 2 35( 650 GeV )2 + Plot this in the plane of the adimensional free parameters (M 1/2, m 0 )/µ: M allowed experimentally excluded m 0 Μ excluded vev 0 excluded by LHC excluded vev

17 Bayesian MonteCarlo technique Scan over all adimensional parameters (m0/µ, B0/m0,..., λt) compatible with measured mt. Compute tan β and msusy from VMSSM. Normally msusy MZ ; rare accidents can make it bigger. All possible fine-tunings are included without using any explicit FT parameter. E.g. focus point is fine-tuning of λt allowed 300 gluino mass in GeV M1 2 in GeV excluded by LHC excluded by LEP m0 in GeV Black dot = excluded spectrum naturalness probability Red = excluded by LHC. Green = allowed

18 Fraction of alive CMSSM 1/ any m h 10. after LEP m h 100 GeV 4. after LEP m h 110 GeV 1. after LEP 3. after LHC 1.5 after LHC 0.7 after LHC (The CMSSM prediction for m h can be circumvented; the theoretical uncertainty in m h is about 3 GeV)

19 M Z m SUSY late SU(2) breaking The scale Q 0 at which RGE running makes m 2 h (Q) < 0 must be close to m SUSY soft terms renormalization scale in GeV SUSY little Higgs as pseudo-goldstone of some symmetry broken at Q 0?

20 The sliding m SUSY model Assume that m SUSY is a free parameter determined by minimizing V MSSM (!) { 0 msusy > Q min V MSSM 0 m 4 SUSY m SUSY < Q 0 Prediction [hep-ph/ , BS]: m SUSY < Q 0 and a loop factor above M Z : dµ 2 u d ln µ sin2 β + dµ2 d d ln µ cos2 β 2 dµ2 ud d ln µ sin β cos β = M 2 Z cos2 2β one loop m 2 h RGE loop factors are big: roughly this means m t 4πM Z/ GeV Predicted: dashed line in the CMSSM plot. Allowed: from 50% to 6% with LHC. PS: BS hypothesis may be BS: V V MSSM. Alternative interpretation in terms of anthropic pressure (Q 0 m SUSY ): more rare than SM? M 1 2 in GeV m 0 in GeV

21 Conclusions These beautiful ideas and the history of the Michelson-Morley experiment teach us that a negative experimental search can have deep theoretical implications. History repeats itself, first as tragedy, second as farce.

22 Conclusions Now this is not the end. It is not even the beginning of the end. But it is, perhaps, the end of the beginning.