ATLAS ResultsM. Cobal, INFN & University Udine

PART IIXXIV SEMINARIO NAZIONALE

di FISICA NUCLEARE E SUBNUCLEARE

OTRANTO, Serra degli Alimini,

21-27 Settembre 2012

Why Mtop and MW are interesting?

2

Mtop , MW and EW precision measurements = cross check of SM and constrain MH

EW fit dominating uncertainties: ΔMtop and ΔMW

For ΔMW not to be the dominant error in the EW fit:

ΔMW 0.007∼ ΔMtop

EWK fit

3

Private communication M. Grunewald:

adding mH=125 ± 2 GeV to the EWK fit:- gives χ2 / Ndf = 17.95 / 14, Prob = 20.9%

Extending the concept to a BSM framework,

Key SM background processes

4

The typical analysis

5

• Design a selection at a given mass maximizing an estimator (eg s/√bkg). Often cutting the phase-space in many regions

• Compute the expected SM background from control samples, side bands, etc.. also with the help from MC simulation (shapes). Assess the systematic error.

• Evaluate the signal efficiency using SM Higgs MC simulation

• Compute with statistical methods the largest signal cross section one can accommodate in the data.

The typical plot

6

• Analyses optimized for exclusion.The result is expressed at a given mass as exclusion at 95% of a cross section

• The excluded cross section is computed in unit of SM cross section (μ).

• Expected sensitivity: measures how performing is the analysis

• The colored bands give the expected statistical⊕systematic variation of the result wrt to the “expected”

• Nearby points are correlated depending on the mass resolution

H → gg

7

Composition of gg sample:

• 75-80% QCD gg production• 20-25% g-jet or jet-jet, jet mis-ID eg due to hard p0

Separation of g-po in Lar Calo• g pointing to locate primary vertex

H → gg

8

H → ZZ*→ 4 leptons (e,m)

9

Golden channel: few events but small background. Good mass resolution

H → WW*→ enmn

10

Combined Significance

11

Significance of the p-value

13

• 5.9 (ATLAS) and 4.9 (CMS) σ excess

• Impressive consistency between 7TeV and 8TeV data

The LHC discovery

14

Heinemeyer et al,Implications of LHC results for TeV-scale physics: signals of electroweak symmetry breaking,Submitted to the Open Symposium of the European Strategy Preparatory Group.

A=ATLASC=CMS√ = channel analyzed

most of the LHC sensitivity comes from

The LHC discovery

15

ATLAS and CMS: significance driven by the γγ, ZZ and WW channels

Besides the excess at 125-126 GeV: 95% CL exclusion of a SM-like Higgs up to ~600 GeV

Properties of the new boson

16

• Mass

• spin and parity ( JP )

• CP (even, odd, or admixture?)

• couplings to vector bosons: is this boson related to EWSB, and how much does it contribute to restoring unitarity in WLWL scattering

• couplings to fermions- is Yukawa interaction at work?- contribution to restoring unitarity?

• couplings proportional to mass ?

• is there only one such state, or more?

• elementary or composite?

• self-interaction

Signal strenght

Mass vs Signal strenght

18

• Mass compatibility between different channels estimated with 2D likelihood, fitting simultaneously μ and mH in each channel

• Probability that a single boson produces mass peaks in H→γγ and H→4l separated by more than the amount observed is 20%

• Mass measurement: performed using profile likelihood ratio with mH floating (channels used: H→γγ and H→4l with separate μ parameters)

• Main systematics from energy scale

expected precision at the LHC: ~100 MeVexpected precision at a linear collider: 40-50 MeV≾

JP and CPSTATUS AND QUESTIONS:

• decay to two photons: cannot be spin 1 (Landau-Yang theorem)

• JP: currently tested at the LHC, using angular correlations in ZZ*, WW* and γγ

• JP: by end of 8 TeV run, assuming 35/fb per exp: ~4 σ separation of 0+ vs 0- and 0+ vs 2+

• CP: more tricky, basic question of possible mixture of CP-even and CP-odd

• If focus at LHC stays on WW*, ZZ* and VBF: limited sensitivity to distinguish pure CP-even state from admixture CP-even / CP-odd

• Linear collider: threshold behaviour of e+e-→ttH gives precision measurement of CP mixing.

arXiv:1208.4018v1 [hep-ph

JP: LHC 2012 prospects

for 35/fb per exp.

Projections

20

coupling scale factors:5-10% with 300/fb at 14 TeV

ratios of partial widths: 5-30%, for luminosities up to 3/ab

very rare channels H→μμ accessible at the 20% level, with a HL-LHC

Higgs self-coupling(double-Higgs production): currently under study.3σ/exp possible at HL-LHC, and 30% prec. on λHHH possible if more channels added and exps. combined

1. I The fundamental symmetries:

Are there more general symmetries than SU(3)C SU(2)L U(1)Y ?

Of course we will be happy to include the gravity in the extend theory.

2. Astrophysics observations:

- Neutrino oscillations

- Dark matter

- Dark Energy

3. The standard model problems:

- Higgs NO unitarity violation

New interactions to cancel this amplitude;

- Higgs YES hierarchy problem for the higgs mass

Beyond the SM

21

Pf < L

Supersymmetry

22

Minimal MSSM

23

Minimal Supersymmetric Standard Model

24

ATLAS SUSY strategy

Search in every corners of the SUSY phase space

Status of SUSY searches

1. Inclusive searches

2. Natural SUSY

3. Long lived particles

4. RPV

Minimal Supersymmetric Standard Model

SUSY theory phase space MSSM: 29 sparticles+5 Higgs undiscovered

Goal: find hints of (N)MSSM particles in the 100 GeV – 1 TeV range

Status of exotic searches

Conclusions

• Probed a wide variety of SUSY – motivated final states

• Nothing found so far, but developed detailed understanding of BG, prerequisite for a discovery

• Transinioning to targeted searches, optimized for specific well-motivated models (eg: natural SUSY)

• Strong push on naturalness dedicated searches for L=2-4.7 fb-1• Direct sbottom & stop• Gluino mediated stop/sbottom• Direct Gauginos [Also sensitive to direct slepton !]

• Analyses of 8 TeV data are in progress. Expect 20 fb-1 of data by the end of the year.