Searching for Non-Colored SUSY at CMS. Alfredo Gurrola Vanderbilt University Dark Matter Workshop at Mitchell Institute TAMU, May 25, 2016

Transcription

1 Searching for Non-Colored SUSY at CMS Alfredo Gurrola Vanderbilt University Dark Matter Workshop at Mitchell Institute TAMU, May 25,

2 30,000,000,000,000,000,000,000 stars in 350 billion large galaxies and 7 thousand billion dwarf galaxies April 6, 2011 Probing Supersymmetric Cosmology at the LHC 2

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6 Content of the Universe

7 Particle Physics & Cosmology pure Bino pure Wino pure Higgsino 7 The identity of dark matter is one of the most profound questions at the interface of particle physics and cosmology.

8 VBF DM Cosmology 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 Some problems can be solved if the DM is nonthermal. For thermal DM, some problems can be solved by adding coannhilation, resonance effects, etc. Determining the composition of the LSP for a given mass is very important to understand early universe cosmology 8

9 Particle Physics & Cosmology How much Bino, Wino, and Higgsino for the DM? It is important to directly probe the EWK SUSY sector in order to determine their DM connection 9

10 10 Current Dark Matter Searches

11 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 1 st /2 nd squarks and gluinos to ~ 1.8 TeV and ~ 800 GeV for stops/sbottoms 11

12 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

13 Why 3 rd Generation SUSY? 13 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 )

14 14 Opposite-sign Di-tau Search OS chargino production Baseline Selections At least one opposite-sign tau pair (e+t h, m+t h, t h +t h ) et h : p T (e/t h ) > 25/25 GeV, h < 2.1/2.3 mt h : p T (m/t h ) > 20/25 GeV, h < 2.1/2.3 t h t h : p T (t h ) > 45 GeV, h < 2.1 m(t 1 t 2 )>15 GeV & Z-mass veto Veto events w/ extra e/m & b s (in some cases) MET > 30 GeV, M T2 > 40 GeV min{df(t h /jet,met)} > 1 Signal Regions t h t h : M T2 > 90 GeV (SR1); M T2 < 90 GeV + Sm T th > 250 GeV (SR2) et h /mt h : M T2 > 90 GeV & m T th > 200 GeV (SR3/SR4) SUS

15 15 Backgrounds Opposite-sign Di-tau Search SUS Top pair, W+jets, QCD, Z+jets, VV, Higgs Estimate of Real Tau Backgrounds Z tt: validate good modeling by MC using control samples w/ low M T2 & near Z-mass Other small BGs taken from simulation Estimate of Fake Tau Background lt h : measure fake rate in fake/jet dominated control sample (MET < 30 GeV) t h t h : Signal-like fake dominated control sample using SS non-iso t h t h is weighted using transfer factor to go from non-iso SS to isolated OS t h t h, measured at low M T2 /mt

16 Opposite-sign Di-tau Search No excess above the SM predictions in any signal region 16

17 Opposite-sign Di-tau Search No excess above the SM predictions in any signal region Fully hadronic ditau is the most sensitive channel 17

18 Opposite-sign Di-tau Search No significant excess above SM predictions in any signal region SUS 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

19 19 Tri-Lepton Search

20 3 rd gen & Compressed No sensitivity in cases with 3 rd gen and compressed spectra Can be important for cosmology 20 Tackling these scenarios is a very tall tall task at the LHC

21 Probing SUSY DM with VBF Cold dark matter candidate 0 ~ 1 Z / h / 0 ~ 1 ~ ~ 0 0 ~ 1 Z / h / 0 ~ 1 Forward tagging jets f MET + jj 21 h

22 Probing EWK SUSY with VBF Cold dark matter candidate Forward tagging jets t t f MET + jj + leptons 22 h

23 Compressed SUSY with VBF Pure Wino/Higgsino dark matter scenarios are special ~ 0 ~ 1 ~ 1 DM M ~ M ~ 0 ( 1 ) ( 1 ) ~ 100 MeV Br( ~ ~ 0 ) ~ 100% P T ( 1 1 ) ~ DM ~ 100 MeV Final state once again jj+met! ~ ~ 0 jj, ~ ~ jj also contribute! 23

24 Probing EWK SUSY with VBF 24 Phys. Rev. D 87, (2013)

25 Probing SUSY DM with VBF 25 Phys. Rev. Lett. 111, (2013)

26 VBF SUSY Kinematics MET > 75 GeV & TeV scale M jj provides 10 4 rejection power! 26

27 First Ever VBF SUSY Search! SUS Forward tagging jets t t f 27 h MET + tt + leptons 8 final states considered: mmjj, emjj, mt h jj, t h t h jj (OS & LS) m/e channels use a single muon trigger; t h t h jj channels use a ditau trigger

28 First Ever VBF SUSY Search! Summary of event selection criteria for all channels 28 Perform a fit of the entire M jj spectrum (shape based search) SUS

29 VBF SUSY BG Estimation As a general rule of thumb, the basic strategy/approach is: 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 29 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 M jj shapes

30 VBF SUSY BG Estimation SUS

31 VBF SUSY Search Results Yields in OS Signal Regions Yields in LS Signal Regions 31

32 VBF SUSY Search Results ~, ~ 1 m ~ ) m( ~ t ) ( ~ 1 ~t 1 5 GeV t ~ 0 m( 1 ) 0 GeV (large mass gap) ( ~ ) ( ~ 0 m 1 m 1 ) 50 GeV (compressed) t 1 1 ( ~ ~ ( ) ( ~ 0 m t1) m 1 m 1 ) 2 2 ~, ~ ~ 1 ~t 1 t t 32

33 VBF SUSY Search Results VBF SUSY search nicely complements other searches for EWK SUSY sector SUS Sensitivity to compressed regions difficult to probe with other searches 33

34 VBF Dark Matter Search SUS First search for direct DM production via VBF! Most stringent limits on compressed colored sector with 8 TeV data

35 35 EWKino Search with ZW

36 Summary 36 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!