Focus-Point studies at LHCFocus-Point studies at LHC

U. De Sanctis, T. LarU. De Sanctis, T. Lari, C. Tronconi, C. TronconUniversity of Milan and INFNUniversity of Milan and INFN

ATLAS CollaborationATLAS Collaboration

SUSYSUSY and and Dark Matter Dark Matter

DM SUSY• Non-baryonic matter density, computed from WMAP measurements:

0.094 < 0.094 < DM DM hh22 < 0.129 (2 < 0.129 (2 conf confidence interval))

For any specFor any specific set of parameters of a SUSY R-parity conserving model, it is

possible to compute the LSP relic density from the mass spectrum and the Big-Bang

cosmology. The relic density can be less than DM (if other contributions to the DM).

The WMAP upper limit is a constrain that defines cosmologically interesting

regions of the SUSY parameter hyperspace. I will limit myself to mSUGRA here. SUSY DMOnce (if) we will have a measurement of SUSY mass spectrum mixing angle etc., one can compute the relic density it corresponds to.

mSUGRA and DMmSUGRA and DM

SUSY spectrum computed with ISAJET 7.69 Relic density computed with Micromegas 1.3.0

Focus Point

Coannihilation(very narrow)

In most of mSUGRA parameter space the predicted relic densityis too large.

In the Focus-Point region(large m0) the lightest neutralino has a significantHiggsino component, and the relic density is reduced by s-channel annihilation in the early universe.

Selected for a detailed study with ATLAS simulation.

Comparison of RGE codes Comparison of RGE codes

m0 scanm1/2 = 300 GeV tan= 10 A0=0 mt=175 GeV

h2

m0 (GeV)3000 4000

Large differences in the predicted relic density using different codesto compute SUSY mass spectrumat the Electro-Weak scale. The study presented here was made using ISAJET 7.69.

SUSY mass spectrumSUSY mass spectrum

102.6102.6

157.4157.4

172.3172.3

290.5290.5

145.4145.4

2282.782.7

gg 854854

qqLL 34163416

tt11 20412041

hh 118. 8118. 8

~

~

~

~

~

~

~

~

~

Masses (GeV)Mass spectrum at the selected pointM0=3400 GeV m1/2 = 300 GeV tan= 10 A0=0 mt=175 GeV

Squarks at the limit of LHC reach. Other sleptons and heavy Higgs too heavy for LHC.Gluino decays into neutralinos and charginos.

Production xSectionProduction xSection

ProductProduction xSections

4.6 pb4.6 pb

gggg 0.50.588 pb pb

qgqg 3.7 fb3.7 fb

• production most abundant, but little jet and missing energy:difficult to separate from SM. We are investigating the possibility to use ±

1→

l± l+ l-

searching for 3 leptons+missing energy+no jet events.• gluino pair production dominant after standard SUSY cuts.• squarks visible with high luminosity

~~

~~

~~

Standard cuts (not optimized for this point) on jet and missing energy and lepton veto.

10 fb-1 (1st LHC year?)Susy/√SM = 16

Sum of jet and missing transverse energy.using ATLAS fast simulation

Gluino decaysGluino decays

Gluino decays:Gluino decays:

g → g → qq 7.2 %qq 7.2 %

g → g → bb 3.7 %bb 3.7 %

g → g → tt 28.0 %tt 28.0 %

g → g → g 5.9 % g 5.9 %

g → g → qqqq 9.6 % 9.6 %

g → g → tb 45.6 %tb 45.6 %

Golden channel is the neutralino dilepton decay (gives neutralino mass difference).In principle, the leptons from neutralino decays can be combined with jets to get further mass relations.However, large number of jets from gluino decay (heavy combinatory background) and poor lepton statistics to start with.We have concentrated on reconstruction of the two main gluino decays using tt and tb invariant mass distributions (gives difference between gluino and gaugino mass scales)

Neutralino dilepton decays:

→ l l

→

l l

Dilepton mass distributionsDilepton mass distributions

~

~~

~

Cuts: Meff > 750 GeV, ETmiss > 100 GeV,

1 jet with pT > 100 GeV Leptons with pT > 10 GeV

At generator level

→

l+l-

→

l+l-

Mll (GeV)604020

Experimental, flavour subtracted

~

~ ~

300 fb-1

No SM background

Mll (GeV)604020 80

The edge can be measured (constrain

on neutralino mixing matrix from the shape?)The

edge hardly visible even after three years at design luminosity.

ATLAS

ATLAS

Gluino decays to charginoGluino decays to chargino

33 fb-1 no SM backg.

Mtb (GeV)200 400 600

30 fb-1

No SM background

M(g)-M

M(g)-M

Top quark decay into udb or csb fully reconstructed. tb invariant masses reconstructed.

ATLAS

Gluino to neutralinoGluino to neutralino

At generator level Experimental, flavour subtracted

g→ tt

g→ tt

g→ tt

g→ tt

~ ~

~ ~

~~

~~

Mtt (GeV) Mtt (GeV)400 600 800 400 600 800

Invariant mass of two fully reconstructed tops.Analysis cuts similar to the gluino to chargino analysis.With high luminosity an endpoint can be extracted.

300 fb-1

No SM background

ATLAS ATLAS

Scan of parameter spaceScan of parameter space

M0-m1/2 scan for mt=175 GeV,A0=0,tan=10,>0

As one moves up the FP strip the SUSY masses increase and the production cross sections decrease.

FP2FP2 FP3FP3 FP4FP4 FP5FP5

MM00 34003400 42004200 57205720 60006000

MM1/21/2 300300 500500 10001000 10001000

hh22 .059.059 .026.026 .07.0788 .012.012

M(g)M(g) 885454 13341334 24532453 24624688

M(M( 103103 176176 401401 241241

(gg)(gg) 558080 21.321.3 0.050.05 0.050.05

46004600 10741074 5757 448080

gq)gq) 3.73.7 0.20.2 00 00

Cross sections in fb, masses in GeV

FP2FP3

FP4 FP5

Gluino massino mass

Neutralino mass differencesNeutralino mass differences

MM

MM

The is close in mass to

on the right of the band (where << WMAP) while it is close to the

on the left of the band (where WMAP). Almost always m(

)-m() is below the threshold for

→Z0

The dilepton edge would provide a good constrain on

Effect of top massEffect of top mass

As the top mass is increased the FP region moves to larger values of m0. For the same m1/2 the gluino/gaugino masses and decays depend very little on the top mass. Sfermions are within LHC reach only for a light top.

M0 (GeV)

M0 (GeV)

M1/

2 (G

eV)

M1/

2 (G

eV)

2000 5000

2000 5000 2000 4000

500

500 500

100

100 100

Mt = 172 GeV

Mt = 175 GeV

Mt = 178 GeV

Effect of top mass Effect of top mass

At fixed m1/2 = 300 GeV, relation between mtop and m0 for the FP region. tan=10,A0=0,>0

FP6FP6 FP2FP2 FP7FP7 FPFP88

mmtoptop 172172 175175 171788 118383

MM00 19001900 34003400 71307130 3030858500

MM1/21/2 300300 300300 300300 300300

hh22 .066.066 .059.059 .07.0777 .0.0882727

M(g)M(g) 881414 858544 904904 10111011

M(M( 102102 103103 101088 106106

(gg)(gg) 703703 558080 412412 202202

46104610 46004600 36503650 44130130

gq)gq) 110110 3.73.7 00 00

FP8

FP7

FP2

FP6

Effect of tanEffect of tantan=10 tan=54

tan=30A larger value of tanpushes the FP band to lower values of m0

At FP11 abundant squark production!

FP2

FP9

FP11

FP10

ConclusionsConclusions

Part of the Focus-Point region is accessible by the LHC experiments. A testpoint was studied with the ATLAS detector fast simulation. A number of mass constrains can be measured: m(

)-m(), m(g)-m(±) and m(g)-m(0).

A scan of mSUGRA focuspoint space has been performed with ISAJET to study how the SUSY mass spectrum varies and select points for more detailed studies.

The gluino gets heavier as one moves along the band in the m0-m1/2 plane. The LHC reach to observe gluino pair production should be about m1/2 ~ 900 GeV. Gaugino production may be used to extend this reach, assuming it can be isolated from the SM background.

The neutralino spectrum is sensitive to position both along and trasversal to the band.

The squarks are accessible for low top masses and/or high tan this would allow to get m0 (and confirm that sfermions are there…)

The Focus-Point is under active study by the ATLAS collaboration. All results are preliminary and more are coming.

Horizontal line scan (III)Horizontal line scan (III)

Not really any good solutNot really any good solutiion won with ith SOFTSUSYSOFTSUSY

Comparison of RGE codes (2) Comparison of RGE codes (2)

Comparison for pointM0=3400 GeV m1/2 = 300 GeV tan= 10 A0=0 mt=175 GeV

ISAJET 7.69ISAJET 7.69 SOFTSUSY 1.SOFTSUSY 1.8686 SPheno 2.22SPheno 2.22 Suspect 2.3Suspect 2.3

M(M( 102.6102.6 126.9126.9 126.9126.9 127.0127.0

M(M( 157.4157.4 247.7247.7 24248.68.6 247.4247.4

M(M( 172.3172.3 596.4596.4 665.4665.4 5580.880.8

M(g)M(g) 8853.753.7 858.1858.1 8807.707.7 869.0869.0

M(uM(uLL)) 3419 3419 34348181 34313431 34348181

All masses in GeVin GeV

One more tableOne more table

FP12FP12 FP2FP2 FP9FP9 FP10FP10 FPFP1111

mmtoptop 1010 1010 3030 5454 5454

MM00 34003400 34003400 24002400 23002300 14001400

MM1/21/2 300300 300300 300300 300300 118800

-- ++ ++ ++ ++

.061.061 .059.059 .091.091 .052.052 .114.114

M(g)M(g) 854854 885454 829829 825825 517517

M(uM(uLL)) 34163416 34163416 24492449 23562356 14351435

M(tM(t11)) 20412041 20412041 14791479 14271427 860860

M(M( 111111 103103 107107 101077 6688

(gg(gg++gq)gq) 580580 558080 700700 13141314 1667016670

45504550 46104610 46004600 36503650 44130130

Little effect from changing the sign of mh = 114.8 GeV