Searches for electroweak production of supersymmetric gauginos and sleptons with the ATLAS detector Christopher Bock on behalf of the ATLAS Collaboration SUSY5 - August 7, 5
Introduction Outline Introduction to EW SUSY Definition of the term electroweak SUSY General analysis strategy Focus of this talk New ATLAS EW SUSY Results Direct stau production Same-sign chargino pair production vector boson fusion Compressed spectra in direct gaugino or slepton pair production All results shown are part of a comprehensive summary paper on EWK SUSY production to be submitted soon (ATLAS-SUSY-4-5) Christopher Bock, LMU München ATLAS EW SUSY Searches
Introduction Term: electroweak production of SUSY Production of colorless gauginos and/or sleptons Why at LHC? Naturalness suggests low mass higgsinos and stops Stringent limits have already been put on strong production with masses above TeV Characteristics Lower σ at LHC than strong prod. Leptonic final states favored Clean signatures, small SM backgrounds - - -3 e e* Electroweak SUSY Electroweak prod. o + l el e* o g t t * q q q q * 4 6 8 4 6 m average [GeV] q g g g σ tot [pb]: pp SUSY S = 8 TeV Here R-parity conserved LSP neutral and stable Optimization for simplified models Christopher Bock, LMU München ATLAS EW SUSY Searches 3
Introduction General Analysis Strategy Searching for rare processes in a flood of SM processes. SUSY searches rely on an accurate modelling of SM backgrounds. Standard Model Backgrounds Reducible E.g. fake taus in a di-tau analysis Analysis dependent data-driven estimation Irreducible E.g. Z ττ in a di-tau analysis Dominant sources: normalised to data in dedicated control regions (CRs) Sub-dominant sources: estimated from MC only In addition predictions are validated in validation regions (VRs) Signal regions (SRs) are defined to discriminate SUSY signal from background. Christopher Bock, LMU München ATLAS EW SUSY Searches 4
L Introduction Focus Focus - ATLAS-SUSY-4-5 Lots of results have already been shown, focus here on new results: Reoptimized search for direct stau prod. Same-sign chargino pair production vector boson fusion Compressed spectra in direct production channels [GeV] m 6 5 4 3 ATLAS m l L / τ / Preliminary + + + L = e/µ/τ l = e/µ m L L / L L / τ L / τ L / τ L / WZ, Wh,, WW, =.5(m = m m = m, τ, τ, τ, + m + m Z lbb+lγγ+l ) -.3 fb, 3L, l, 3L, τ, τ, l+3l, l +3L, l, m s=8 TeV Status: Feb 5 arxiv:4.79 arxiv:43.594 arxiv:4.79 arxiv:47.35 arxiv:47.35 arxiv:43.594 arxiv:5.7 = m arxiv:43.594 + m h = m Expected limits Observed limits 3 4 5 6 7 m m (=m ) [GeV] Christopher Bock, LMU München ATLAS EW SUSY Searches 5
Recent Results Direct stau prod. p τ τ Backgrounds Reducible: bgs containing one or more fake taus, e.g. W +jets, multi-jet p τ τ Irreducible: two or more real prompt taus, e.g. dibosons, t t, Z +jets Two opposite sign taus in the final state Veto light leptons m T > 3GeV Multi Variate Analysis (MVA) optimised to yield best exp. discovery sensitivity (using Boosted Decision Trees, BDTs) Update of: JHEP 4 (4) 96, arxiv:47.35 [hep-ex] Christopher Bock, LMU München ATLAS EW SUSY Searches 6
R Recent Results Direct stau prod. Events /.5 6 5 4 3 Data/MC Events / 4 GeV s = 8 TeV,. fb τ MVA Data multi jet Z+jets W+jets (m,m τr ) = (9, ) GeV Total SM Top quark diboson.4.8.6.4... BDT Score.8.6 8 6 4 SR.8.6.4.. BDT Score s = 8 TeV,. fb τ MVA SR Data multi jet Z+jets W+jets (m,m τr ) = (9, ) GeV Total SM Top quark diboson Events / 3 GeV Events / GeV 8 6 4 4 8 6 4 s = 8 TeV,. fb τ MVA SR Data multi jet Z+jets W+jets (m,m τr ) = (9, ) GeV Total SM Top quark diboson 4 6 8 4 6 8 miss E T [GeV] s = 8 TeV,. fb τ MVA SR Data multi jet Z+jets W+jets (m τ,m ) = (9, ) GeV Total SM Top quark diboson No excess observed Setting limits Dominant syst.: Stat. MC uncert % MET soft-term resolution % W +jets normalization 5 % Total syst.: 35% 5 5 3 35 4 45 m eff [GeV] 3 4 5 6 7 8 9 m T [GeV] Christopher Bock, LMU München ATLAS EW SUSY Searches 7
Recent Results Direct stau prod. The upper limit on the combined production of τ L τ L and τ R τ R could be improved from.95 to.9 for one of the mass points. Christopher Bock, LMU München ATLAS EW SUSY Searches 8
Recent Results Direct stau prod. σ [pb] Simplified Model: + τ τ τ Observed 95% CL Expected 95% CL NLO Theory ( σ) s=8 TeV,. fb m( )= GeV m( )= GeV m( )=4 GeV σ [pb] m( )=6 GeV m( )=8 GeV m( )= GeV 5 5 3 m τ [GeV] 5 5 3 m τ [GeV] 5 5 3 m τ [GeV] 95% CL exclusion limits on the cross-section for combined production of left- and right-handed stau pairs with equal masses for various masses. Christopher Bock, LMU München ATLAS EW SUSY Searches 9
Recent Results SS CC prod. VBF q q W q /l l / l / W l / l / q /l Backgrounds Reducible: bgs containing one or more fake leptons, e.g. W +jets and t t Irreducible: two real prompt leptons, e.g. dibosons and Higgs Charge flip: one or more leptons have mis-measured charge (dedicated CR) Exactly two same sign light leptons, two or more jets, large MET Two leading jets well separated, from opposite sides of the detector and have high inv. mass, VBF-like topology Signal region is defined using a b-jet veto and a number of kinematic variables of leptons and jets Christopher Bock, LMU München ATLAS EW SUSY Searches
Recent Results SS CC prod. VBF Events / 75 GeV Data Total SM s = 8 TeV,.3 fb WW Charge Flip Wγ Reducible miss ZV Others VBF l l jj + E T (m,m )=(,75) GeV (m,m )=(,95) GeV 8 Events /.8 8 s = 8 TeV,.3 fb miss VBF l l jj + E T Data Total SM WW Charge Flip Wγ Reducible ZV Others (m,m )=(,75) GeV (m,m )=(,95) GeV 6 4 6 4 No excess observed Setting limits Events / 3 GeV 8 7 6 5 4 3 4 6 8 4 m jj [GeV] s = 8 TeV,.3 fb miss VBF l l jj + E T Data WW Wγ ZV Total SM Charge Flip Reducible Others (m,m )=(,75) GeV (m,m )=(,95) GeV Events /.5 GeV 8 7 6 5 4 3 3 4 5 6 7 η jj s = 8 TeV,.3 fb miss VBF l l jj + E T Data WW Wγ ZV Total SM Charge Flip Reducible Others (m,m )=(,75) GeV (m,m )=(,95) GeV Dominant syst.: Fake factor closure test 3% Stat. uncert. on reducible bg % Total syst.: % 5 5 3 35 miss E T [GeV] 5 5 5 3 35 l p [GeV] T Christopher Bock, LMU München ATLAS EW SUSY Searches
Recent Results SS CC prod. VBF σ [fb] 3 Simplified Model: s = 8 TeV,.3 fb jj l ( l) jj l Observed limit Expected limit ( σ exp ) LO Theory σ jj σ [fb] 3 Simplified Model: s = 8 TeV,.3 fb jj l ( l) jj l Observed limit Expected limit ( σ exp ) LO Theory σ jj SS VBF m( ) = GeV m = (m + m )/, l SS m( VBF ) = GeV m = (m + m )/, l 5 5 5 3 35 m m [GeV] 5 5 5 3 35 m m [GeV] 95% CL upper limits on the cross-section for VBF production of. The limits have been set with respect to the mass difference between the and the. Current analysis cannot exclude expected SUSY cross section, however an interesting approach has been developed for probing compressed Electroweak SUSY scenarios with more data in Run-. Christopher Bock, LMU München ATLAS EW SUSY Searches
Compressed Scenarios Brief Introduction Reoptimized ATLAS analyses to target compressed spectra: Two OS Light Leptons Two SS Light Leptons Three Light Leptons Motivation Lots of SUSY models favor compressed sparticle mass spectra. Difficulties Low mass splittings soft decay products SM-like Christopher Bock, LMU München ATLAS EW SUSY Searches 3
Compressed Scenarios p p l l l l Backgrounds Two OS Light Leptons Reducible: bgs containing one or more fake leptons, e.g. W +jets Irreducible: two real prompt leptons, e.g. dibosons, Higgs, Z+jets Two opposite sign light leptons b-jet veto, Z veto using inv. mass of lept pairs Two SRs requiring a high p T ISR jet, sensitive to small and moderate mass splittings Use super-razor variables, sensitive to mass differences between sparticles Christopher Bock, LMU München ATLAS EW SUSY Searches 4
Compressed Scenarios Two SS Light Leptons p p l/ l/ /l l/ l/ l/ Backgrounds Reducible: bgs containing one or more fake leptons, e.g. W +jets Irreducible: two real prompt leptons, e.g. dibosons, triboson, Higgs Charge flip: one or more leptons have mis-measured charge (dedicated CR) Two same sign well isolated light leptons Eight BDTs are trained to cover four different mass splittings for m =, 35, 65, GeV m For each splitting: one region requiring one ISR jet and one applying a jet veto Christopher Bock, LMU München ATLAS EW SUSY Searches 5
Compressed Scenarios Three Light Leptons p p l/ l/ /l l/ l/ l/ Backgrounds Reducible: bgs containing one or more fake leptons, e.g. W /Z+jets, WW, top and t t Irreducible: three real prompt leptons, e.g. WZ/ZZ, triboson, Higgs Exactly three light leptons, one same flavor OS pair (SFOS) b-jet veto, Υ veto using mass of SFOS pair Two SRs use low p T leptons to target mass splittings of 4-5 and 5-5 GeV, two further SRs request a jet with p T > 5GeV to target ISR events for both splitting regions Christopher Bock, LMU München ATLAS EW SUSY Searches 6
Compressed Scenarios Events /.5 Data/SM 5 4 3.5.5 Two OS leptons 8 s = 8 TeV,.3 fb 7 SRl a SF channel 6 Data Total SM WW Others Top quark Reducible ZV (m, m ) = (, 8) GeV (m, m ) = (, 35) GeV..3.4.5.6.7.8.9 R Events / GeV Data/SM 3 Three leptons s = 8 TeV,.3 fb Data Reducible.5 3 4 5 6 7 8.5 3 4 5 6 7 8 miss E T [GeV] WZ (m,m Total SM ZZ Others )=(,85) GeV SR3L a Events /.4 radian Data/SM 4 3 Results Two SS leptons 6 Data Reducible 5 s = 8 TeV,.3 fb VV(V) ISR VR Charge Flip Total SM Wγ Higgs, ttv (m, m ) = (,9) GeV (m, m ) = (6,4) GeV.5 Observable.5.5.5.5 3 miss Φ(jet,E ) [rad] T Events / 5 GeV 8 s = 8 TeV,.3 fb 7 SRl b SF channel 6 5 4 3 Data Total SM Others Top quark WW Reducible ZV (m, m ) = (, 8) GeV (m, m ) = (, 35) GeV Events /. radians 4 3 s= 8 TeV,.3 fb Data Reducible WZ (m Total SM ZZ Others,m )=(3.5,7.5) GeV SR3L a Events / 37.5 GeV 6 Data Reducible 5 s = 8 TeV,.3 fb Charge Flip no ISR VR VV(V) 4 3 Total SM Wγ Higgs, ttv (m, m ) = (,9) GeV (m, m ) = (6,4) GeV Data/SM.5.5 3 4 5 6 7 8 9 R M [GeV] Data/SM.5.6.7.8.9 3 3. 3..5.5.5.6.7.8.9 3 3. 3. miss φ(e T, Jet) [radians] Data/SM.5 Observable.5 5 5 5 3 lep m T [GeV] Christopher Bock, LMU München ATLAS EW SUSY Searches 7
Compressed Scenarios Interpretation Two OS light leptons σ [pb] + Simplified Model: l( l) l s = 8 TeV,.3 fb m = x*m, l m( ) = GeV l NLO Theory ( σ) Observed Limit Expected Limit x =.5 x =.5 x =.5 x =.75 x =.95 [GeV] m Simplified Model: l ( l) l 45 SUSY Observed limit ( σ theory ) 4 s = 8 TeV,.3 fb Expected limit ( σ exp ) m = (m + m )/ Observed limit l,, l 35 arxiv:43.594 SRl 3 5 5 m = m 5 3 3 4 5 6 m [GeV] 5 5 3 35 4 45 5 55 m [GeV] Reoptimized analysis nicely complements the already published one in the region of low mass splittings close to the diagonal :) Christopher Bock, LMU München ATLAS EW SUSY Searches 8
l L l L l Compressed Scenarios Interpretation [GeV] m 4 8 6 4 Simplified Model: l l L l( L m m SUSY Observed limit ( σtheory ) Expected limit ( σ exp ) Observed limit 3l Observed limit 3l = (m = m m + m )/ = m Two SS light leptons and three light leptons ), l l L l ( arxiv:4.79 soft/isr ) l s=8 TeV,.3 fb l l ( ) Combined SS MVA, 3l, 3l soft/isr [GeV] m 6 5 4 3 Simplified Model: l l ), l l ) l L l ( L l( L l l ( m = m +.95*(m m ) m = m s=8 TeV,.3 fb Combined SS MVA, 3l m = m ) SUSY Observed limit ( σ ) theory Expected limit ( σ exp ) Observed limit 3l Observed limit SS MVA σ [pb] s = 8 TeV,.3 fb 3 Simplified Model: l L l L l( ), l l L l ( 3l ) l m = x * m l l ( m( ) = GeV ) NLO Theory ( σ) Observed Limit Expected Limit x =.5 x =.5 x =.5 x =.75 x =.95 8 4 6 8 4 [GeV] m 3 4 5 6 7 8 [GeV] m 4 3 4 5 6 7 m [GeV] Reoptimized analysis nicely complements the already published one in the region of low mass splittings close to the diagonal :) Christopher Bock, LMU München ATLAS EW SUSY Searches 9
Compressed Scenarios Interpretation pmssm, NUHM, GMSB M [GeV] 3 5 45 M = 5 GeV, tan β = ( GeV) (3 GeV) (4 GeV) [GeV] m / 5 45 4 NUHM: m =5TeV,tanβ=5,A =.6m,m =TeV,µ> A s=8 TeV,.3 fb Combined l, 3l, 4l tan β 6 5 GMSB: M mess =5 TeV, N =3, µ >, C = 5 grav Theory excl. 4 35 3 5 5 s = 8 TeV,.3 fb Combined l, 3l, Wh SUSY Observed limit ( σ ) theory Expected limit ( σ exp ) Observed limit l, 3l LEP (3.5 GeV) arxiv:43.594 5 5 3 35 4 45 5 3 µ [GeV] 35 3 5 5 SUSY Observed limit ( σ ) theory Expected limit ( σ exp) LEP (3.5 GeV) Observed limit l Observed limit 3l Observed limit 4l 5 5 3 35 4 45 5 µ [GeV] 4 3 s=8 TeV,.3 fb 4l Observed limit SUSY ( σ ) theory Expected limit ( σ exp ) Observed limit SS/3 l + jets arxiv:44.5 4 5 6 7 8 9 3 Λ [TeV] Combination (doing a combined fit) of existing, published, analyses shows a nice improvement in sensitivity :) Christopher Bock, LMU München ATLAS EW SUSY Searches
L L Conclusion and Outlook [GeV] m 6 5 4 3 ATLAS m l L / τ / Preliminary + + + L = e/µ/τ l = e/µ m L L / L L / τ L / τ L / τ L / WZ, Wh,, WW, =.5(m = m m = m, τ, τ, τ, + m + m Z Before lbb+lγγ+l ) -.3 fb, 3L, l, 3L, τ, τ, l+3l, l +3L, l, m s=8 TeV Status: Feb 5 arxiv:4.79 arxiv:43.594 arxiv:4.79 arxiv:47.35 arxiv:47.35 arxiv:43.594 arxiv:5.7 = m arxiv:43.594 + m h m = m Expected limits Observed limits ) [GeV] m( 6 5 4 3 ATLAS + 3 Preliminary m l L / l L / τ L / l L / τ L / l R = m τ τ Now l, arxiv:43.594 SRl τ, arxiv:47.35 SS MVA + 3l soft/isr + 3l τ 3l+4l + 3l.3 fb, m s=8 TeV Expected limits Observed limits m l L/ τ = m / =.5(m + m ) 3 4 5 6 7 m ) [GeV] (=m 3 4 5 6 7 m(,, ) [GeV] 3 Lots of effort has been put into searching for SUSY Many different methods have been developed Strong and ew. prod. of SUSY have not been observed, yet Limits have been set Time to unveil SUSY throughout run Christopher Bock, LMU München ATLAS EW SUSY Searches
L L Conclusion and Outlook [GeV] m 6 5 4 3 ATLAS m l L / τ / Preliminary + + + L = e/µ/τ l = e/µ m L L / L L / τ L / τ L / τ L / WZ, Wh,, WW, =.5(m = m m = m, τ, τ, τ, + m + m Z Before lbb+lγγ+l ) -.3 fb, 3L, l, 3L, τ, τ, l+3l, l +3L, l, m s=8 TeV Status: Feb 5 arxiv:4.79 arxiv:43.594 arxiv:4.79 arxiv:47.35 arxiv:47.35 arxiv:43.594 arxiv:5.7 = m arxiv:43.594 + m h m = m Expected limits Observed limits ) [GeV] m( 6 5 4 3 ATLAS + 3 Preliminary m l L / l L / τ L / l L / τ L / l R = m τ τ Now l, arxiv:43.594 SRl τ, arxiv:47.35 SS MVA + 3l soft/isr + 3l τ 3l+4l + 3l.3 fb, m s=8 TeV Expected limits Observed limits m l L/ τ = m / =.5(m + m ) 3 4 5 6 7 m ) [GeV] (=m 3 4 5 6 7 m(,, ) [GeV] 3 Lots of effort has been put into searching for SUSY Lots of different methods have been developed Strong and ew. prod. of SUSY have not been observed, yet Limits have been set Time to unveil SUSY throughout run Thank you for your attention! Christopher Bock, LMU München ATLAS EW SUSY Searches
Backup BACKUP Christopher Bock, LMU München ATLAS EW SUSY Searches 3
Backup Variables Christopher Bock, LMU München ATLAS EW SUSY Searches 4
Backup Variables Christopher Bock, LMU München ATLAS EW SUSY Searches 5
Backup Variables Ref : arxiv: 3.487 Christopher Bock, LMU München ATLAS EW SUSY Searches 6
Backup Direct stau BDT vars Christopher Bock, LMU München ATLAS EW SUSY Searches 7