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Relic Density at the LHC

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The coannihilation channel occurs in most SUGRA models with non-universal soft breaking, ... t PAIRS AND CATEGORIZE THEM AS OPPOSITE SIGN (OS) OR LIKE SIGN (LS) ... – PowerPoint PPT presentation

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Title: Relic Density at the LHC


1
Relic Density at the LHC
B. Dutta
In Collaboration With
R. Arnowitt, A. Gurrola, T. Kamon, A. Krislock,
D.Toback
Phys.Lett.B63946,2006, hep-ph/0608193 (Phys.
Lett.B), To appear
2
SUSY in Early Stage at the LHC
The signal to look for 4 jet missing ET
3
Example Analysis
Kinematical Cuts and Event Selection
  • ETj1 100 GeV, ETj2,3,4 50 GeV
  • Meff 400 GeV (Meff ? ETj1ETj2ETj3ETj4
    ETmiss)
  • ETmiss Max 100, 0.2 Meff

Phys. Rev. D 55 (1997) 5520
4
Relic Density and Meff
SUSY scale is measured with an accuracy of 10-20
  • This measurement does not tell us whether the
    model can generate the right amount of dark
    matter.
  • The dark matter content is measured to be 23
    with an accuracy of less than 5 at WMAP
  • Question

To what accuracy can we calculate the relic
density based on the measurements at the LHC?
5
Strategy
  • We establish the dark matter allowed regions
    from the detailed features of the signals.
  • We accurately measure the masses.
  • We calculate the relic density and compare with
    WMAP.

6
Dark Matter Allowed Regions
We choose mSUGRA model. However, the results can
be generalized.
  • Neutralino-stau coannihilation region
  • A-annihilation funnel region This appears for
    large values of m1/2
  • Focus point region the lightest neutralino has
    a larger higgsino component

7
Relic Density Calculation
In the stau neutralino coannihilation region
Griest, Seckel 91
8
Coannihilation, GUT Scale
In mSUGRA model the lightest stau seems to be
naturally close to the lightest neutralino mass
especially for large tanb
For example, the lightest selectron mass is
related to the lightest neutralino mass in terms
of GUT scale parameters
Thus for m0 0, becomes degenerate
with at m1/2 370 GeV, i.e. the
coannihilation region begins at
m1/2 (370-400) GeV
For larger m1/2 the degeneracy is maintained by
increasing m0 and we get a corridor in the m0 -
m1/2 plane.
The coannihilation channel occurs in most SUGRA
models with non-universal soft breaking,
9
Coannihilation Region
tanb 40, m 0, A0 0
Can we measure DM at colliders?
10
SUSY at LHC
Signals
In Coannihilation Region of SUSY Parameter Space
Soft t
Final state 3/4 tsjets missing energy
11
Observables
Use Hadronically Decaying t and construct 3
observables
  • Sort ts by ET (ET1 ET2 ) and use
  • OS-LS method to extract t pairs from the decays

2. Use Counting Method (NOS-LS) Ditau
Invariant Mass (Mtt) to measure mass
difference
3. Measure the PT of the low energy t
12
SUSY Parameters
Since we are using 3 variables, we can measure
DM, Mgluino and the universality relation of
the gaugino masses i.e.
Mgluino measured from the Meff method may not be
accurate for this parameter space since the tau
jets may pass as jets in the Meff observable.
The accuracy of measuring these parameters are
important for calculating relic density.
13
Mttvis in ISAJET
Version 7.69 (m1/2 347.88, m0 201.06) ?
Mgluino 831
Chose di-t pairs from neutralino decays with (a)
h
14
ETmiss 1j 3t Analysis Path
Extracting t Pairs from Decays
EVENTS WITH CORRECT FINAL STATE 1t 3j ETmiss
APPLY CUTS TO REDUCE SM BACKGROUND (Wjets,
) ETmiss 100 GeV, ETj1 100 GeV,
ETmiss ETj1 400 GeV
ORDER TAUS BY PT APPLY CUTS ON TAUS WE EXPECT
A SOFT t AND A HARD t PTt 40, 40, 20 GeV,
LOOK AT t PAIRS AND CATEGORIZE THEM AS OPPOSITE
SIGN (OS) OR LIKE SIGN (LS)
OS FILL LOW OS PT HISTOGRAM WITH PT OF SOFTER
t FILL HIGH OS PT HISTOGRAM WITH PT OF HARDER t
LS FILL LOW LS PT HISTOGRAM WITH PT OF SOFTER
t FILL HIGH LS PT HISTOGRAM WITH PT OF HARDER t
LOW OS-LS
LOW OS
LOW LS
HIGH OS
HIGH LS
HIGH OS-LS
15
ETmiss 1j 3t Analysis
3 t1 Jet
Much smaller SM background, but a lower
acceptance 1 ISAJET PGS sample of ETmiss, 1
jet and at least 3 taus with pTvis 40, 40, 20
GeV and et 50, fake (fj?t ) 1. Final cuts
ETjet1 100 GeV, ETmiss 100 GeV, ETjet1
ETmiss 400 GeV 2 Select OS low di-tau mass
pairs, subtract off LS pairs
Small dependence on the uncertainty of fj?t
Note fj?t 0 ? 1.6 counts/fb-1
16
3 t1 Jet (contd)
  • Next combine NOS-LS and Mtt values to measure DM
    and Mgluino simultaneously

Mass rises with Mgluino
Counts drop with Mgluino
dDM/DM 15 and dMgluino/Mgluino 6
17
ETmiss 2j 2t Analysis Path
EVENTS WITH CORRECT FINAL STATE 2t 2j ETmiss
APPLY CUTS TO REDUCE SM BACKGROUND (Wjets,
) ETmiss 180 GeV, ETj1 100 GeV, ETj2
100 GeV, ETmiss ETj1 ETj2 600 GeV
ORDER TAUS BY PT APPLY CUTS ON TAUS WE EXPECT
A SOFT t AND A HARD t PTall 20 GeV, PTt1
40 GeV
LOOK AT t PAIRS AND CATEGORIZE THEM AS OPPOSITE
SIGN (OS) OR LIKE SIGN (LS)
OS FILL LOW OS PT HISTOGRAM WITH PT OF SOFTER
t FILL HIGH OS PT HISTOGRAM WITH PT OF HARDER t
LS FILL LOW LS PT HISTOGRAM WITH PT OF SOFTER
t FILL HIGH LS PT HISTOGRAM WITH PT OF HARDER t
LOW OS-LS
LOW OS
LOW LS
HIGH OS
HIGH LS
HIGH OS-LS
18
ETmiss 2j 2t Analysis
1 ISAJET ATLFAST sample of ETmiss, 2 jets,
and at least 2 taus with pTvis 40, 20 GeV and
et 50, fake (fj?t ) 1. Optimized cuts
ETjet1 100 GeV ETjet2 100 GeV ETmiss
180 GeV ETjet1 ETjet2 ETmiss 600 GeV 2
Number of SUSY and SM events (10 fb-1) Top 115
events Wjets 44 events SUSY 590 events
19
2t Analysis Discovery Luminosity
10-20 fb-1
Negligible fj?t dependence
5
-5
Assumption The gluino mass is measured with
dM/Mgluino ?5 in a separate analysis.
A small DM can be detected in first few years of
LHC.
20
PTsoft in ISAJET
PT STUDY
Phys.Lett. B639 (2006) 46, hep-ph/0603128
Slope of PT distribution contains ?M Information.
Slope of the soft t PT distribution has a DM
dependence
21
ETmiss 2j 2t Analysis PTsoft
1 ETmiss , at least 2 jets, at least 2 ts
with PTvis 20, 40 GeV 2 et 50 , fake rate
1 3 Cuts ETjet1 100 GeV, ETjet2 100 GeV,
ETmiss 180 GeV ETjet1 ETjet2 ETmiss
600 GeV
OS
OS-LS
LS
22
PT Study
Can we still see the dependence of the PT slope
on DM using OS-LS Method?
23
Slope of PT
Measuring DM from the PT Slope
  • Luminosity 40 fb-1

24
Slope of PT ? DM
  • How accurately can DM be measured for our
    reference point?
  • Considering only the statistical uncertainty

We can measure DM to 6 accuracy at 40 fb-1
12 accuracy at 10 fb-1 for mass of
831 GeV.
25
Model Parameters
  • Can parameterize the our observables as
    functions of DM, ,
  • NOS-LS , to first order, does not depend on
    mass. A large increase or decrease
  • in mass is needed to obtain a point
    that lies outside the error bars
  • Cross-Section is dominated by the gluino mass

26
Model Parameters
27
Testing Gaugino Universality
CONTOURS OF CONSTANT VALUES ( L 40
fb-1 )
  • Intersection of the central contours
  • provides the measurement of DM,
  • ,
  • Auxilary lines determine the 1s
  • region
  • 1st order test on Universality

28
Determination of m0 and m1/2
DM and Mgluino ? m0 and m1/2 (for fixed A0 and
tanb)
We determine dm0/m0 1.2 and dm1/2/m1/2 2
(for A00, tanb40)
29
Determination of
DM and Mgluino ? (for fixed A0 and tanb)
dWh2/Wh2 7 (for A00, tanb40)
30
Conclusion
  • Meff will establish the existence of SUSY
  • Different observables are needed to establish
  • the dark matter allowed regions in SUSY model at
    the LHC
  • Analysis with visible ETt 20 GeV establishes
    stau-neutralino coannihilation region
  • 2t analysis Discovery with 10 fb-1
  • d DM /DM 5 , d mg /mg 2 using Mpeak,
    NOS-LS and pT
  • Universality of gaugino masses can be checked

The analyses can be done for the other models
that dont suppress c20 production.
  • dWh2/Wh2 7 for A00, tanb40
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