Desperately Seeking SUSY

Transcription

1 Desperately Seeking SUSY Ben Allanach a (University of Cambridge) Please ask questions while I m talking a BCA, Gripaios, ; BCA, Sridhar

2 Supersymmetric Copies H

3 Supersymmetric Copies H 2 H 2

4 Review of R-Parity The superpotential of the MSSM can be seperated into two parts: W Rp = h e ijl i H 1 Ē j +h d ijq i H 1 Dj +h u ijq i H 2 Ū j +µh 1 H 2, W RP = 1 2 λ ijkl i L j Ē k +λ ijkl i Q j Dk λ ijkūi D j Dk +κ i L i H 2. W Rp is what is usually meant by the MSSM. Q: Why ban W RP? A: Proton decay

5 Definition of R-Parity Q: How is W RP normally banned? A: By defining discrete symmetry R p R p = ( 1) 3B+L+2S. SM fields have R p = +1 and superpartners have R p = 1. There are two important consequences: Because initial states in colliders arer p EVEN, we can only pair produce SUSY particles The lightest superpartner is stable

6 Candidate Event: High E T (j)

7 Natural SUSY The particles coupling the most strongly to the higgs are the stops a. Minimising the MSSM Higgs potential, M2 Z 2 δm 2 H 2 µ 2 +m 2 H 2, 3h2 t 4π2 m2 t ln ( ΛUV m t ) t H 2 t H 2 H 2 H 2 g H 2 t H 2 a M. Papucci, J. T. Ruderman and A. Weiler, arxiv: ; C. Brust, A. Katz, S. Lawrence and R. Sundrum, arxiv:

8 Natural SUSY The particles coupling the most strongly to the higgs are the stops a. Minimising the MSSM Higgs potential, M2 Z 2 δm 2 H 2 µ 2 +m 2 H 2, 3h2 t 4π2 m2 t ln ( ΛUV m t ) No cancellation < < m t 700 GeV, m g 1000 GeV. Experimental E T searches m t > 500 GeV, m g > 900 GeV. a M. Papucci, J. T. Ruderman and A. Weiler, arxiv: ; C. Brust, A. Katz, S. Lawrence and R. Sundrum, arxiv:

9 g t: E T > 50/120 GeV, N b 2, #j 2, H T > 320 GeV

10 Direct Stop Seach

11 Jets Plus E T Search

12 Bottom Up Implications of 2012 Data Naturalness is under pressure. Ways to get around it: First two generation squarks> 1.8 TeV, m t = TeV, m g = TeV, m χ 0 1 < 0.5 TeV. Ruled out soon? Compressed spectra a : ISR monojets/ E T searches give you m g > 500 GeV only. RPV decreases/removes the E T b. Explains why natural SUSY hasn t been found yet Like-sign dileptons is a generic signature, as we ll see a Dreiner, Kramer, Tattersall arxiv: b BCA, Gripaios arxiv:

13 RPV and Dark Matter If one gives up R parity,χ 0 1 is no longer a good dark matter candidate, since it decays. One then has to have something else, eg: Gravitino - still decays, but lifetime may be much longer than the age of the universe Hidden sector matter Axion/axino The implications of each of these is that (in-)direct dark matter searches shouldn t find anything.

14 Upper Bounds onλ ijk

15 Bottom up thinking We are not assuming MSSM: don t put higgs constraints - there might be higher dimension operators coming from heavier fields. Some specific (or even generic) string model. We only put in the particles important for our analysis. Others may be decoupled, or light: it shouldn t matter.

16 Gluino/stop production at LHC7 1e gluino stop σ prod NLO /pb mass/gev

17 Gluinos With R p Violation We assume lightish g, t R. If one has lepton number violatinglle orlh 1 operators, the gluinos decay producing various leptons. These cases ought to be easy to find, and are good candidates for searches. Get same-sign leptons. With LQD operators, the stops will again decay into leptons, easy to see. Flavour constraints imply that L 3 QD operators are likely to be the largest. Get same-sign leptons in 7 9 of g g events. With UDD operators, the (right-handed) top decays direcly into jets.

18 Baryon Number Violating Example g g t t t b d j d j Can lead to natural SUSY with light stops and gluinos that hasn t been excluded yet. A difficult case a : W λ ijk U id j D k. a BCA and Ben Gripaios, arxiv: t b g g production dominates. Here, you can look for like-sign di-leptons since gluinos decay into t and t with equal branching ratios.

19 Other Light States How robust is the same-sign dilepton signature in the case that other states are also light?

20 Can we avoid SS dileptons? For m H ± > m t +m b, H + t b dominates, which again will yield same-sign dileptons. H + τ + ν τ is also OK, since we ll get like-sign di-taus. Only fly in the ointment comes from Fig. 1c: when H + c b (but only happens when tanβ m t V cb /m τ 3, which seems unlikely).

21 Same-sign E T Limits CMSSll1 a : H T > 400 GeV, E T > 120 GeV a CMS-PAS-SUS-010; ATLAS-CONF

22 A FB in the Standard Model 1.96 TeVp p collisions at the Tevatron. A FB = N(c > 0) N(c < 0),c = cosθ. N(c > 0)+N(c < 0) SM Prediction:

23 Measurements ofa FB S Leone (CDF) talk at Electroweak session of Rencontres de Moriond 2012.

24 Other Constraints σ LHC7 t t = 173.4±10.6 pb, σ SM t t = 163±10 pb A y C = N( y t > y t ) N( y t > y t ) N( y t > y t )+N( y t > y t ) = 0.015±0.04, wherey i = 1/2ln(E i p i z)/(e i +p i z) is the rapidity of particlei. A y CSM = 0.006±0.002.

25 A FB Many models of random particles have been proposed, but most don t fit all the data. However, this one does: W = λ t Rd R b R λ 313 d R (p 1 ) t R (q 1 ) br d R (p 2 ) t R (q 2 ) λ 313 Figure 1: SUSY contribution to A FB a a BCA, Sridhar arxiv:

26 New Physics Contribution d σ dc = λ βŝ 384π α s λ β 72ŝ [ (βc 1) ŝ(βc 1)+2m 2 t 2m 2 br 4m 2 t +ŝ(βc 1) 2 ŝ(βc 1)+2m 2, t 2m 2 br ] 2 + whereβ = 1 4m 2 t/ŝ, ŝ = (p 1 +p 2 ) 2, α s is the strong coupling constant andm t is the top quark mass.

27 Calculate observables with MadGraph arxiv: Allanach and Sridhar, 2012 A FB m sbottom /TeV λ Allanach and Sridhar, m sbottom /TeV A C y

28 Constraints and Predictions < A FB < < A y C < < σt t TEV /pb < < σt t TEV (bin)/fb< < A l FB < < Ah FB < < σt t LHC7 /pb < 39.2 Table 1: 95% CL constraints < A FB < < A y C < < σt t TEV /pb < < σt t TEV (bin)/fb< < A l FB < < Ah FB < < σt t LHC7 /pb < < σt t LHC8 /pb < 33 Table 2: Predicted values in good fit region

29 Summary R p violation allows natural SUSY with lightish gluinos and squarks that have not yet been ruled out by searches. Same-sign dilepton searches without huge E T cut will be interesting. It covers almost all possible cases of RPV operator. In case of U i D j D k operators, current searches m g > 550 GeV. AnomalousA FB measurements can also be explained by U i D j D k type operator - fits all data Other models tend to fail one or more checks

30 Backup

31 Technical Hierarchy Problem A problem with light, fundamental scalars. Their mass receives quantum corrections from heavy particles in the theory: F h λ λ h cλ2 d n k 16π F 2 k 2 m F Quantum correction to Higgs mass: m phys h = m tree h +O(m F /100). m F GeV/c 2 is heaviest mass scale present. Higgs is eaten by W,Z to giveo(m W,Z ) 90 GeV/c 2 m tot < 1 TeV/c 2. h

32 Symmetry Standard model gauge symmetry is internal, but supersymmetry (SUSY) is a space-time symmetry. We call extra SUSY generatorsq, Q. Q fermion boson Q boson fermion In the simplest form of SUSY, we have multiplets ( ) ( ) spin 0 spin 1/2,, spin 1/2 spin 1 where each spin component in the multiplet should have identical quantum numbers (except spin).

33 Supersymmetric Solution Exact supersymmetry adds 2 scalars f L,R for every massive fermion with m fl,r = m F and they couple to h with the same strength: f L,R + h F λ λ h = 0 h λ 2 h F Q: Where are the selectrons?

34 Supersymmetric Solution Exact supersymmetry adds 2 scalars f L,R for every massive fermion with m fl,r = m F and they couple to h with the same strength: f L,R + h F λ λ h = 0 h λ 2 h F Q: Where are the selectrons? A: SUSY must be softly broken.

35 Supersymmetric Solution Exact supersymmetry adds 2 scalars f L,R for every massive fermion with m fl,r = m F and they couple to h with the same strength: f L,R + h F λ λ h = 0 h λ 2 h F When we break SUSY, we must make sure that we don t reintroduce the naturalness problem: soft breaking.

36 Soft breaking Make scalar partners heavier than fermions: m 2 fl,r = m 2 F +δ2 Then we find a quantum correction to m h of (Drees) ( ) m 2 h λ2 4δ 2 +2δ 2 ln m2 F +O(δ 4 ). 16π 2 µ 2 So, ifδ < O(1) TeV/c 2, there s no fine tuning in m h.

37 Soft breaking Make scalar partners heavier than fermions: m 2 fl,r = m 2 F +δ2 Then we find a quantum correction to m h of (Drees) ( ) m 2 h λ2 4δ 2 +2δ 2 ln m2 F +O(δ 4 ). 16π 2 µ 2 So, ifδ < O(1) TeV/c 2, there s no fine tuning in m h. We should see supersymmetric particles in the Large Hadron Collider.

38 Broken Symmetry 3 components of the Higgs particles are eaten by W ±,Z 0, leaving us with 5 physical states: h 0,H 0 (CP+), A 0 (CP-), H ± SUSY breaking and electroweak breaking imply particles with identical quantum numbers mix: ( B, W3, H 0 1, H 0 2 ) χ0 1,2,3,4 ( t L, t R ) t 1,2 ( b L, b R ) b 1,2 ( τ L, τ R ) τ 1,2 ( W ±, H ± ) χ ± 1,2

39 Electroweak Breaking Both Higgs get vacuum expectation values: ( ) ( ) ( ) ( H 0 1 v1 H H2 0 H 1 v 2 ) and to get M W correct, match with v SM = 246 GeV: β v SM v 2 tanβ = v 2 v 1 v 1 L = h t t L H 0 2 t R +h b bl H 0 1 b R +h τ τ L H 0 1 τ R m t sinβ = h tv SM 2, m b,τ cosβ = h b,τv SM 2.

40 Hierarchy problem solved The supersymmetric copies cancel the quantum fluctuations. (This is a very difficult problem to solve). Not only that, the model contains a dark matter candidate the neutralinoχ 0 1: Weakly interacting Stable Massive To predict how much of it is around today, we must make assumptions on our cosmology, and on the particle physics. If we can measure the particle physics, we have a handle on the cosmology.

41 Sets of Cuts Signal Region m µµ /GeV σ test SSµµ /fb A/10 3 σ 95 SSµµ /fb ATLASµµ1 > ATLASµµ2 > ATLASµµ3 > ATLASµµ4 > Table 3: search regions. The ATLAS same-sign di-muon analysis

42 Sets of Cuts Signal Region p miss T /GeV m T(l 1 )/GeV A/10 3 σ 95 SSll /fb ATLASll1 > 150 > ATLASll2 > 150 > Table 4: ATLAS same sign-di lepton analysis search regions.

43 Sets of Cuts Signal Region H T /GeV p miss T /GeV N ll/fb A ǫ/10 3 N 95 ll CMSll1 >400 > <3.7 CMSll2 >400 > <8.9 CMSll3 >200 > <7.3 Table 5: Number of events past cuts for the CMS same sign-di lepton analysis N ll predicted by our test point over SM backgrounds, and acceptance A times efficiency ǫ of the signal selection, for the test point.

44 Test Point m g = 588 GeV, m t = 581 GeV LH panel: E T /GeV, RH panel: H T /GeV

45 Test Point m g = 588 GeV, m t = 581 GeV LH panel: p T (j 1 )/GeV, RH panel: p T (l 1 )/GeV

46 Test Point m g = 588 GeV, m t = 581 GeV LH panel: N J, RH panel: N isol e,µ

47 Efficiencies of CMSll E T SUSY events past cuts ǫ = SUSY events You pay for the di-leptonictt branching ratio. m gluino /TeV Allanach and Gripaios, m stop /TeV ε/%