I. Looking for SUSY under the LHC Lamppost (towards a complete - PowerPoint PPT Presentation

I. Looking for SUSY under the LHC Lamppost (towards a complete classification of SUSY signatures) Konstantin Matchev In collaboration with: P. Konar, M. Park, G. Sarangi, Phys. Rev. Lett. 105 (2010) 221801; 1111.asap Interpreting LHC Discoveries workshop 1 GGI, Florence, November 10, 2011

Outline of this talk • The latest fashionable models? No. – Any given model is surely wrong • Supersymmetry (SUSY) in general (no prejudice!). – theoretical motivations • gauge unification • hierarchy problem – experimental motivations • not ruled out • dark matter candidate – sociological motivations • popular, must learn for final exam, competition is doing it... • looks like many other models anyway Cheng,KM,Schmaltz 2002 • This talk: a fresh new look at SUSY phenomenology 2

Number of relevant Number of Theory constructs event topologies parameters under study Theory of Everything, by assumption one? NA simplification e.g. string theory a few all SUSY breaking “model” General MSSM way too many all simplification by relevance pMSSM JoAnne’s talk nineteen all a SUSY “hierarchy” a few a few This talk one “Simplified model” Jay’s talk a few 3

What is needed for LHC collider phenomenology? • Theory models? No. – those were important to get funding – will become important again after a discovery • Event topologies (a.k.a. simplified models). – specified by a skeleton Feynman diagram (A->B->C->...) – relevant parameters: masses, widths, rate – not really a new idea: From LEP2 SUSY WG ADLO M � (GeV/c 2 ) 0.08 100 Neutralino Mass (GeV/c 2 ) + - e ˜ e ˜ 100 Selectrons R R � s = 183-208 GeV Observed Cross Section U.L. (pb) 0.07 � s = 183-208 GeV 80 Observed 80 0.06 ADLO Preliminary Expected 0.05 60 60 0.04 40 40 0.03 0.02 20 20 0.01 ( " =-200 GeV, tan � =1.5) Excluded at 95 ! CL 4 0 0 0 50 60 70 80 90 100 50 60 70 80 90 100 Selectron Mass (GeV/c 2 ) M e (GeV/c 2 ) ˜ ) �

SUSY under the lamppost • The first LHC discovery may not be in the TDR • It will be easier to make a discovery if – there are many new particles to be discovered – the new particles are colored (produced with QCD-type cross-sections) – the signal involves (lots of) How isolated, high P T leptons many? • Look for new physics under the lamppost – also find what new physics away from the lamppost looks like

Main building blocks • Standard Model • Supersymmetry Fermions Bosons Bosons Fermions ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ Squarks Gauginos ~ ~ ~ ~ ~ ~ ~ Higgsinos Sleptons • Spins and couplings fully predicted by SUSY 6 • Masses of the new particles completely unknown

SUSY signatures depend on • Quantitative factors: require parameter space scans. – value of SUSY masses themselves pMSSM scan: 2 19 =524288 • size of the cross-sections • relative contribution of strong vs. electroweak production – SUSY mass splittings • phase space suppression factors in the BR’s • hardness of the SM decay products, efficiency of cuts • Qualitative factors: requires considering permutations – the hierarchical ordering of the SUSY particles • The parameter space is infinite, the number of permutations is finite! Let’s study all permutations first! 7

Mass parameter space factorization Parameter space All possible Overall scale of the masses permutations and mass splittings of n particles (“hierarchies”) R n / S n R n S n ⊗ = infinite finite infinite Let us study this part! • Example: n=2 Konar,KM,Park,Sarangi 2010 x 2 x min (x 1 ,x 2 ) ⊗ or = (x 2 ,x 1 ) 8 x max x 1

The SUSY parameter space • The relevant parameters are the physical masses – taken directly at the weak scale, no need to run any RGE’s TABLE I: The set of SUSY particles considered in this anal- ysis, shorthand notation for each multiplet, and the corre- sponding soft SUSY breaking mass parameter. u L , ˜ ˜ h ± , ˜ ˜ u , ˜ ˜ h 0 h 0 b 0 w ± , ˜ w 0 ˜ d L u R ˜ d R e L , ˜ ˜ ˜ e R ˜ g ˜ ν L d L Q U D L E H B W G Q M Q M U M D M L M E M H M B M W M G B D W E H U G 9 mass

SUSY collider signatures • There are 9!=362,880 possible permutations • First: who is the LSP (lightest superpartner) – CHAMP (8!=40,320) if LSP=E – R-hadron (4x8!=161,280) if LSP=G, Q, U or D – Missing energy (4x8!=161,280) if LSP=L, H, W or B • Second: who is the LCP (lightest colored particle) – most abundantly produced at hadron colliders • Third factor: what is the dominant decay of the LCP – count suppressions by multibody phase space – count suppressions from “ino” mixing angles x . . . x C y . . . y L , 10

Strong production cross-section Konar,KM,Park,Sarangi 2011 • Does the LCP cross-section really dominate? – compare the inclusive production of gluinos and squarks M G M G M G 2-LCP 2-LCP 1-LCP 1-LCP 0-LCP 0-LCP 600 100 600 100 U 600 100 U U M M M gluino U L squark 550 90 550 90 550 90 LCP 500 80 500 80 500 80 LCP 450 70 450 70 450 70 400 60 400 60 400 60 350 50 350 50 350 50 300 40 300 40 300 40 U R squark 250 30 250 30 250 30 200 LCP 20 200 20 200 20 150 10 150 10 150 10 100 0 100 150 200 250 300 350 400 450 500 550 600 100 0 100 0 M 100 150 200 250 300 350 400 450 500 550 600 100 150 200 250 300 350 400 450 500 550 600 Q M M Q Q 2 LCP + X 1 LCP + X 0 LCP + X 11

SUSY decay modes • Couplings already determined by SUSY – mixing angles are typically small; degeneracies are rare – branching ratios uniquely predicted G or Q U D ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ L E Squarks Gauginos ~ ~ ~ ~ ~ W B ~ ~ Higgsinos Suppression H Decay product Sleptons none jet lept on mild W ± /Z/h strong 12

Counting suppression factors G G G Q Q Q U U U L E L E L E W B W B W B H H H a) 2-body decays, no MAS b) 2-body decays, with MAS c) 3-body decays, no MAS G G G Q Q Q U U U L E L E L E W B W B W B H H Suppression H Decay product none jet d) 3-body decays, with MAS e) 4-body decays, no MAS lept on mild W ± /Z/h strong f) All 13

LCP decays: an example W B L H Q start G Q or U D E U D G L E • A variation of the travelling salesman problem W B • Several possible paths: Suppression H Decay product none jet end lept on – QBH, QWH: give jet plus V mild W ± /Z/h strong – QBLH, QWLH, give jet plus 2L • Count all such “dominant” signatures for each permutation 14

LCP decays: another example start G B G Q or U D E H U L D W Q L E • This example is trivial end • Single unique path: W B Suppression H Decay product – GB: gives 2 jets none jet lept on mild • Recall the simplified model W ± /Z/h strong from Jay’s talk 15

LCP decays: yet another example start H L E B G G Q or U D U D Q W L E • This example is also trivial end • Single unique path: W B Suppression H Decay product – GB: gives 2 jets none jet lept on mild – G to L is a 4 body decay W ± /Z/h strong – G to E is a 4 body decay – G to H is a 3 body decay with mixing angle suppression 16

LCP decays: yet another example U H L W E B start G Q or U D D G Q L E • MSUGRA-like example end • Single unique path: W B Suppression H Decay product – UB: gives 1 jet none jet lept on mild – U to L is a 3 body decay W ± /Z/h strong – U to E is a 3 body decay – U to W suppressed by mixing 17 – U to H suppressed by mixing

LCP decays: yet another example Q W B L start G Q or U D U D G E H L E • Two paths: end – QWLB: gives 1 jet plus 2L W B – QB: gives only 1 jet Suppression H Decay product none jet • Which path to choose? lept on mild W ± /Z/h strong – both – the one with more leptons • “maximally leptonic signature” 18

Counting signatures • Counting all possible dominant LCP decays TABLE II: Number of hierarchies for the various dominant decay modes of the LCP C . n v = 0 n v = 1 n v = 2 n j = 1 n j = 2 n j = 1 n j = 2 n j = 1 n j = 2 n � x 2 0 79296 26880 12768 3360 1344 672 1 30240 10080 1824 480 192 96 2 19770 6030 1500 180 0 0 3 4656 1296 312 72 6 6 4 1656 396 66 6 0 0 8 lepton events! • Only the maximally leptonic dominant LCP decays TABLE III: Number of hierarchies for the maximally leptonic decay modes of the LCP C . n v = 0 n v = 1 n v = 2 n j = 1 n j = 2 n j = 1 n j = 2 n j = 1 n j = 2 n � 0 61488 21168 8310 2550 780 420 x 2 1 24150 8310 1278 378 132 72 2 17190 5550 1230 150 0 0 3 4362 1242 312 72 6 6 4 1656 396 66 6 0 0 19 8 lepton events!

MSUGRA result • Only 47 out of the 161,280 possible hierarchies • Only 4 out of the 26 possible decay channels. 20

An example with 4 leptons Q W L B H E start G Q or U D U G D L E • Maximally leptonic path: – QWLBEH: gives 1 jet plus 4L W B • Events with 8 leptons! Suppression H Decay product none jet end lept on mild • Signature jargon: W ± /Z/h strong – 3 leptons: gold plated – 4 leptons: platinum plated 21 – 8 leptons: ???