cp violation at the lhc, boston

Probing SUSY CP ViolationProbing SUSY CP Violationin Stop Decays at the LHCin Stop Decays at the LHC

The

Uni

vers

ity

of M

anch

este

r

Frank [email protected]

University of Manchester

in collaboration with Olaf Kittel (Granada U.)

arXiv:0905.3088 [hep-ph]

SUSY09, Boston, 7 June 2009

7/6/2009Frank Deppisch SUSY CP Violation in Stop Decays at LHC22/22/22

CP ViolationCP Violation

CP violation in quark sector



CP violation in quark sectorCP violation in neutrino sector?



CP violation in quark sectorCP violation in neutrino sector?Baryon Asymmetry of the Universe

→ New mechanism of CP Violation required

B = nB/n = 6.1−0.20.3⋅10−10



CP violation in quark sectorCP violation in neutrino sector?Baryon Asymmetry of the Universe

→ New mechanism of CP Violation requiredSupersymmetry Possible new CP phases in SUSY and SUSY-breaking

Gaugino mass terms → φM1 , φM3

Higgs mixing term → φµ 3rd generation trilinear scalar coupling terms → φAt,b,τ

B = nB/n = 6.1−0.20.3⋅10−10


Bounds from Electric Dipole MomentsBounds from Electric Dipole MomentsStringent bounds from electron and neutron EDMs ∣d e∣4⋅10−27e⋅cm

∣d n∣6⋅10−26e⋅cm


Bounds from Electric Dipole MomentsBounds from Electric Dipole MomentsStringent bounds from electron and neutron EDMs

Generally constrain SUSY phases to be small (or SUSY scale large), e.g. φµ < π/10

∣d e∣4⋅10−27e⋅cm∣d n∣6⋅10−26e⋅cm


Bounds from Electric Dipole MomentsBounds from Electric Dipole MomentsStringent bounds from electron and neutron EDMs

Generally constrain SUSY phases to be small (or SUSY scale large), e.g. φµ < π/10

… unless cancellations occur between contributions

∣d e∣4⋅10−27e⋅cm∣d n∣6⋅10−26e⋅cm

=1°=1°


Triple Product AsymmetriesTriple Product Asymmetries

CP-even observables at colliders sensitive to phasesmassesbranching ratioscross sections




CP-odd observables are needed to confirm CP Violation





Momentum triple product

→ T-odd → CPT Invariance → CP-odd

p1p3

p2

T= p1⋅ p2× p3

− p1

− p3

− p2

Time Reversal





Momentum triple product

→ T-odd → CPT Invariance → CP-odd

CP-odd asymmetry

p1p3

p2

A=N T0−N T0

N T0N T0=∫ sign T ∣M∣2d Lips

∫∣M∣2d Lips

T= p1⋅ p2× p3

− p1

− p3

− p2

Time Reversal


Stop Production at the LHCStop Production at the LHC

FrameworkmSUGRA decorated with CP phases at EW scale

Benchmark Scenario


Stop Production at the LHCStop Production at the LHC

FrameworkmSUGRA decorated with CP phases at EW scale

Benchmark Scenario

Stop pair production at the LHCppt i t i

∗

Stop boost distributionCross section


CP-odd Asymmetries in Stop DecaysCP-odd Asymmetries in Stop DecaysStop cascade decay sensitive to φAt, φµ(, φM1) from spin-spin correlations

20 l L /R

t 1



Triple product asymmetries not Lorentz-invariant

20 l L /R

t 1



Triple product asymmetries not Lorentz-invariant Asymmetry reduction with stop boost

Effect of stop boost on asymmetry

20 l L /R

Alab= 1∫0

∞ d d t

Ad t

t 1


mSUGRA ParametersmSUGRA Parameters

Minimally required luminosity at the LHC to observe 1σ effectBased only on theoretical significance (statistical fluctuation of signal) S≈∣A∣ L

right-h. slepton, t1 2 t , 2l R lleft-h. slepton, t 1 2 t , 2l L l

∣A0∣=500 GeV , tan =5At=3 /4 ,=0


CP Phase SensitivityCP Phase Sensitivity

Asymmetry largely independent of φM1 in mSUGRALarge asymmetries possible for small φAt and φµ

Asymmetry in the lab frame [%]

m0=70 GeV , m1 /2=270 GeV∣A0∣=500 GeV , tan=5

Min. luminosity required at LHCt 1 2 t , 2l R l


ConclusionConclusion

CP Violation in Stop decays at the LHCVia 2nd Lightest NeutralinoTop-Neutralino Spin-Spin CorrelationsSensitive to CP phases φAt and φµ in mSUGRA




Triple Product AsymmetriesCP-odd observables → Signal of CP ViolationAlternative Sensitivity than EDMsDetectable at LHC




Triple Product AsymmetriesCP-odd observables → Signal of CP ViolationAlternative Sensitivity than EDMsDetectable at LHC

Motivation for experimental analysisReconstruction EfficienciesEpsilon Product of Four Momenta

cp violation at the lhc, boston

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