Searching for

Non-Colored

SUSY at CMS

Alfredo Gurrola Vanderbilt University

Dark Matter Workshop at Mitchell Institute TAMU, May 25, 2016

1

April 6, 2011 Probing Supersymmetric Cosmology at the LHC 2

30,000,000,000,000,000,000,000 stars in 350 billion large galaxies and 7 thousand billion dwarf galaxies

Content of the Universe

Particle Physics & Cosmology

pure Bino

pure Wino

pure Higgsino

The identity of dark matter is one of the most

profound questions at the interface of particle physics

and cosmology. 7

LSP has large Wino/Higgsino component

LSP annihilation cross section is too

large to fit observed DM relic density

LSP is mostly Bino

LSP annihilation cross section is too

small to fit observed DM relic density

Determining the composition of the LSP for a given mass is

very important to understand early universe cosmology

Some problems can be solved if the DM is non-

thermal. For thermal DM, some problems can be

solved by adding coannhilation, resonance effects, etc.

VBF DM Cosmology

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Particle Physics & Cosmology

It is important to “directly” probe the EWK SUSY sector

in order to determine their DM connection

How much Bino, Wino, and Higgsino

for the DM?

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Current Dark Matter Searches

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Classic SUSY DM Searches

Determining the mass and content of the LSP

requires model dependent correlations

between colored and non-colored sector (e.g.

grand unification in mSUGRA)

ATLAS and CMS pushing limits on 1st/2nd

squarks and gluinos to ~ 1.8 TeV and ~

800 GeV for stops/sbottoms

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Classic SUSY DM Searches

Colored objects heavy and the

cross-section is small

Started to look at direct production of

EWKinos: small cross-section but

oftentimes cleaner signature

12 No significant improvement in sensitivity with 13 TeV data …

focus today on a few more recent 8 TeV results

Why 3rd Generation SUSY?

Cosmological Motivation Thermal bino DM scenario

LSP annihilation is not enough to provide the correct cold dark matter relic density

Near mass degeneracy between bino LSP and other SUSY particle (e.g. stau) allows coannihilation processes which contribute to the determination of the relic density

WMAP constrains on the relic density constrain DM = M(Stau) – M(LSP) < 50 GeV

Coannihilation of the LSP with e.g. stau provide the correct DM relic density

Left/right-handed sfermion mixing proportional to mass of SM partners

Stau mass eigenstates lighter than other sparticles (“naturalness”)

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http://arxiv.org/pdf/1205.5842v1.pdf

Opposite-sign Di-tau Search

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OS chargino production

Baseline Selections

At least one opposite-sign tau pair (e+th, m+th, th+th)

eth: pT(e/th) > 25/25 GeV, |h| < 2.1/2.3

mth: pT(m/th) > 20/25 GeV, |h| < 2.1/2.3

thth: pT(th) > 45 GeV, |h| < 2.1

m(t1t2)>15 GeV & Z-mass veto

Veto events w/ extra e/m & b’s (in some cases)

MET > 30 GeV, MT2 > 40 GeV

min{Df(th/jet,MET)} > 1

Signal Regions

thth: MT2 > 90 GeV (SR1); MT2 < 90 GeV + SmT

th > 250 GeV (SR2)

eth/mth : MT2 > 90 GeV & mTth > 200 GeV (SR3/SR4)

SUS-14-022

Opposite-sign Di-tau Search

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Backgrounds

Top pair, W+jets, QCD, Z+jets, VV, Higgs

Estimate of Real Tau Backgrounds

Ztt: validate good modeling by MC using control samples w/ low MT2 & near Z-mass

Other small BGs taken from simulation

Estimate of “Fake” Tau Background

lth: measure fake rate in fake/jet dominated control sample (MET < 30 GeV)

thth: Signal-like “fake” dominated control sample using SS non-iso thth is weighted using transfer factor to go from non-iso SS to isolated OS thth , measured at low MT2/mT

SUS-14-022

No excess above the SM predictions in any signal region

Opposite-sign Di-tau Search

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No excess above the SM predictions in any signal region

Fully hadronic ditau is the most sensitive channel

Opposite-sign Di-tau Search

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No significant excess above SM predictions in any signal region

M(chargino) up to ~ 420 GeV excluded for massless LSP

No exclusion on M(chargino) for DM < 150 GeV

Direct stau production remains difficult to probe

Opposite-sign Di-tau Search

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SUS-14-022

Tri-Lepton Search

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3rd gen & Compressed

No sensitivity in cases with 3rd

gen and compressed spectra

Can be important for cosmology

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Tackling these scenarios is a very

tall tall task at the LHC

http://arxiv.org/pdf/1205.5842v1.pdf

Probing SUSY DM with VBF

0

1~

0

1~

0~

0

1~

0

1~

~

// hZ

// hZ

Cold dark matter candidate

h

f

Forward tagging jets

MET + jj

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Probing EWK SUSY with VBF

Cold dark matter candidate

h

f

Forward tagging jets

MET + jj + leptons t t

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Pure Wino/Higgsino dark matter scenarios are special

1~

1~

0~

D

D

MeVMP

Br

MeVMMM

T 100~~)(

%100~)~~(

100~)~()~(

0

11

0

11

Final state once again jj+MET!

jjjj 11

0

11~~ ,~~

also contribute!

Compressed SUSY with VBF

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http://arxiv.org/pdf/1210.0964v2.pdf

Phys. Rev. D 87, 035029 (2013)

Probing EWK SUSY with VBF

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http://arxiv.org/pdf/1304.7779v1.pdf

Phys. Rev. Lett. 111, 061801 (2013)

Probing SUSY DM with VBF

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VBF SUSY Kinematics

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MET > 75 GeV & TeV scale Mjj provides 104 rejection power!

First Ever VBF SUSY Search!

h

f

Forward tagging jets

t t

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SUS-14-005

8 final states considered: mmjj, emjj, mthjj, ththjj (OS & LS) m/e channels use a single muon trigger; ththjj channels use a ditau trigger

MET + tt + leptons

First Ever VBF SUSY Search!

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Summary of event selection criteria for all channels

Perform a fit of the entire Mjj spectrum (shape based search)

SUS-14-005

As a general rule of thumb, the basic strategy/approach is:

Main part of the strategy is how to measure the VBF efficiency

CRs chosen so signal contamination is negligible

Small BGs taken from MC with single SF and systematics based on level of agreement between MC and data Mjj shapes

VBF SUSY BG Estimation

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Very well understood by many non-VBF dilepton

analyses

Uncharted territory. Do not expect the MC to correctly model the VBF efficiency

Validate with BG enhanced control samples use MC

and correct using a SF

Measure the VBF efficiency directly from a high purity

BG enriched sample

VBF SUSY BG Estimation

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SUS-14-005

VBF SUSY Search Results

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Yields in OS Signal Regions Yields in LS Signal Regions

VBF SUSY Search Results

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0

21~,~

0

1~

1~t

t

t

GeV 5)~()~( 11 t mm

d)(compresse GeV 50)~()~(

gap) mass (large GeV 0)~(

0

11

0

1

mm

m

0

21~,~

0

1~

1~t

t

t

)~(2

1)~(

2

1)~( 0

111 t mmm

VBF SUSY Search Results

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VBF SUSY search nicely complements other searches

for EWK SUSY sector

Sensitivity to compressed regions difficult to probe with

other searches SUS-14-005

VBF Dark Matter Search

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SUS-14-019

First search for direct DM production via VBF! Most stringent limits on compressed

colored sector with 8 TeV data

EWKino Search with ZW

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I hope everyone enjoyed this perhaps unconventional CMS talk

Tried to motivate the non-colored SUSY searches at CMS from the standpoint of the interconnection between particle physics and cosmology since we’re here at the Mitchell Institute

Generally speaking, the 2015 data has not yet brought improved sensitivity for the EWK SUSY searches, so focus was placed on a couple of the more recent 8 TeV results … which perhaps might not be so familiar to many of you.

OS ditau search: OS chargino production with decays via staus

Summarized the tri-lepton tau enriched/dominated searches

VBF production of EWKinos with ditau + MET

VBF production of Dark Matter and the use of VBF DM topology to probe compressed spectra.

Summarized EWKino search with Z and W in dilepton + dijet

More analyses I didn’t cover (apologize if I skipped your favorite) and many more new ideas which will be explored with 2016 data

Thanks again to the coordinators for this opportunity!

Summary