A Motivated Non-Standard Supersymmetric Spectrum

Transcription

1 A Motivated Non-Standard Supersymmetric Spectrum Paolo Lodone, EPFL, CH PhD Thesis discussed on December 09, 2011 Scuola Normale Superiore and INFN, Pisa Supervisor: Riccardo Barbieri

2 Outline 1) Introduction: the Hierarchy problem and Supersymmetry 2) Supersymmetry phenomenology without a light Higgs boson 3) Hierarchical sfermions and the SUSY Flavor and CP problems 4) Consequences of a U(2)^3 flavor symmetry 5) Present status 6) A different project: the naturally light dilaton (related with the work of Sergio Fubini)

3 1) Introduction: the Hierarchy problem and supersymmetry What is Naturalness? Introduction to naturalness: e.g. [Luty, ]. 'Philosophical discussion': e.g. [Giudice ] SM as low-energy remnant of a more fundamental theory Parameters of the SM (e.g. mh) determined in terms of the fundamental ones What happens for small change of fundamental parameters? Initial condition at 'input scale' SM parameter Radiative corrections quadratically sensitive to the 'cutoff' Definition of finetuning [Barbieri, Giudice 1988] Idea: protect mh with a symmetry (that must be (among the others) broken at low energy) SUPERSYMMETRY Input scale the highest 'non-symmetric' scale = sparticle masses (motivation for low-energy SUSY)

4 Residual finetuning, or SUSY naturalness in one slide [Barbieri, talk October ] Can gain something by lowering the scale M at which SUSY-breaking is comunicated Reasonable (too optimistic?) requirement: " < 5-10 Minimal requirements: - stops, left sbottom < GeV - higgsinos < GeV - gluino < GeV

5 Crucial (i.e. theorist's favorite #) natural configuration to be tested at LHC: [Barbieri, Pappadopulo ], [Barbieri, recent talks] [Hall, talk Oct ] [Arkani-Hamed, talk Oct ]

6 REF: 2) Supersymmetry phenomenology without a light Higgs boson [PL, Naturalness bounds in extensions of the MSSM without a light Higgs boson 2010] [Barbieri, Bertuzzo, Farina, PL, Pappadopulo, A Non Standard Supersymmetric Spectrum 2010] ; [PL, Supersymmetry without a light Higgs boson but with a light pseudoscalar 2011] Main point: Increased Higgs quartic reduced finetuning SUSY Bottom-up approach: gauge extension or $SUSY [Barbieri et al ] Natural consequence: Higgs mass GeV (now excluded, except maybe if there is mixing, e.g. [Hall et al ]) First two generations can be naturally heavier improved flavor (now also better for direct detection) MSSM after LEP Perturbativity Unification & EWPT (manifest) Naturalness Phenomen. consequences on gluino decays, Higgs properties and DM (no flavor symmetry, only O($) suppr.)

7 3) Hierarchical sfermions and the SUSY Flavor and CP problems REF: [Barbieri, Bertuzzo, Farina, PL, Zhuridov, MFV with hierarchical squark masses 2010] [Bertuzzo, Farina, PL, On the QCD corrections to F=2 FCNC in the Supersymmetric SM with hierarchical squark masses 2010] [Barbieri, PL, Straub, CP violation in Supersymmetry with hierarchical squark masses 2011] Hierachy: SUSY CP problem: better under control with heavy first two generations Flavour: with no degeneracy / alignement: m1,2 > hundreds of TeV Minimal Flavour Violation: Flavour transitions controlled by CKM matrix Problem with flavour blind CPV phases: typically: sin(%)<10 &-10 ' How to keep the good features of both? Pattern: with mh > 5-10 TeV is enough (we also included previously neglected effects)

8 REF: 4) Consequences of a U(2)^3 flavor symmetry [Barbieri, Isidori, Jones-Perez, PL, Straub, U(2) and Minimal Flavor Violation in Supersymmetry 2011] Pattern of masses and mixings Smaller GF, Y not irr. break. terms Flavor-blind phases hierarchical spectrum Motivation for hierarchical squarks and U(2) flavor symmetry Too large FV in original papers extend to U(2)^3. Moreover assume weakly broken in minimal way Consequences: Sufficient flavor protection [Pomarol, Tommasini 1993], [Barbieri, Dvali, Hall 1996], [Barbieri, Hall, Romanino 1997] Definite pattern of deviation from the SM in "F=2: possible to remove CKM tension Predictions (from preferred region in the fit) No more tension

9 5) The LHC data: no NP so far Models motivated by naturalness start being significantly constrained (but not 'dead' yet) [CMS, ]

10 5) Phenomenology of Supersymmetric models in light of the LHC data REF: [PL, Supersymmetry Phenomenology beyond the MSSM after 5/fb of LHC data 2012] 2) Insisting on DM and unification Split SUSY 3) Only elegance strings High-scale SUSY Main question the LHC will(is) answer(ing): is the EW scale finetuned?

11 5) Conclusions SM-like Higgs found Measure its couplings, look for new particles not found Main point: Naturalness Light colored sector coupled mainly to the top (scalar or fermion?) We are here Compositeness no new part., std coupings. non std Higgs coupl and/or new part. Supersymmetry Indication of fundamental Finetuning Naturalness arguments wrong. SUSY, if there, not for naturaln. Most feared by th-ists Landscape-anthropic? Naturalness arg. were Right Is it SUSY? MSSM Or Beyond? Composite? Other? What is flavor like? Exciting possibility Lot of work needed to discriminate.

12 6) Totally different subject, related with Fubini: requirements for a naturally light dilaton [work in progress with Riccardo Rattazzi et al] Question: which are the requirements in order to naturally have a light scalar, identifiable with the dilaton, in a Poincaré-invariant field theory? Why nontrivial: dilaton ( Goldstone boson of spontaneously broken conformal invariance. But Goldstone theorem does not work streightforwardly with spacetime symmetries (dilaton can have quartic potential in 4D) Very starting point is nontrivial: need tuning " = 0 Stay tuned Our purpose: - discuss the conditions under which the dilaton is naturally light - provide holographic 5D realization, elucidating the requirements

13 Backup

14 Outlook: with FLAVOR SM-like Higgs no extra info Flavor tests new flavor effects found not found SM only BSM We are here Measure its couplings, look for new particles no new part., std coupings. non std Higgs coupl and/or new part. SM (and MSSM) ecluded Look for Higgs with reduced couplings and new particles something Is found no Higgs nor new part. (Higgs but no new part.) Indication of fundamental Finetuning Naturalness arguments wrong. SUSY, if there, not for naturaln. Most feared by th-ists Landscape-anthropic? Switch to strings or cond. matter or finance. Naturalness arg. were Right Is it SUSY? MSSM Or Beyond? Composite? Other? What is flavor like? Exciting possibility Lot of work needed to discriminate. We did not understand much about EWSB. New particles beyond LHC reach? Now excluded NP is there, unfortunately beyond LHC reach. Nature is finetuned, maybe not too much. Opportunity to learn something about Flavor

15 2) PH: Supersymmetry phenomenology without a light Higgs boson [P.L. 2010] [Barbieri et al 2010] "SUSY SU(2) U(1) - = scale at which some coupling gets semiperturbative - In gauge extensions is maximized consistently with naturalness of the higher vev [Batra, Delgado, Kaplan, Tait 2004] [Barbieri, Hall, Nomura, Rychkov 2007] With low, mh can be significantly raised

16 2) PH: Supersymmetry phenomenology without a light Higgs boson No degeneracy nor alignement: > hundreds of TeV [Dine, Kagan Samuel 1990] [Pomarol Tommasini 1996] [Cohen, Kaplan, Nelson 1996] If and : See e.g. [Giudice, Nardecchia, Romanino 2009] If as above but :

17 2) PH: Supersymmetry phenomenology without a light Higgs boson

18 2) PH: Supersymmetry phenomenology without a light Higgs boson [Arkani-Hamed, Murayama 1997] M=10 13 TeV M=10 8 TeV MSSM "SUSY with mh=250 GeV M=10 3 TeV Mg=2 TeV Mg=1 TeV Mg=0.5 TeV We neglect lighter gauginos; Mg=gluino mass at low energy.

19 2) PH: Supersymmetry phenomenology without a light Higgs boson See also The well tempered neutralino [Arkani-Hamed, Delgado, Giudice 2006]

20 3) PH: Supersymmetry phenomenology - more focused on Flavor and CP problems REF: [Barbieri, Bertuzzo, Farina, PL, Zhuridov, MFV with hierarchical squark masses 2010] [Barbieri, PL, Straub, CP violation in Supersymmetry with hierarchical squark masses 2011] Assuming sparticles with similar mass ) 500 GeV: B, g Aq=yq A0 md A0* + cedm (both even 1 o.o.m. stronger without exact degenaracy ) Susy CP Problem

21 REF: 3) PH: Supersymmetry phenomenology - more focused on Flavor and CP problems [Barbieri, Bertuzzo, Farina, PL, Zhuridov, MFV with hierarchical squark masses 2010] [Barbieri, PL, Straub, CP violation in Supersymmetry with hierarchical squark masses 2011]

22 3) PH: Supersymmetry phenomenology - more focused on Flavor and CP problems REF: [Barbieri, Bertuzzo, Farina, PL, Zhuridov, MFV with hierarchical squark masses 2010] [Bertuzzo, Farina, PL, On the QCD corrections to F=2 FCNC in the Supersymmetric SM with hierarchical squark masses 2010] FC couplings all weighted by CKM: Effective MFV: m# Bounds (Mk, #k):

23 REF: We imposed "F=2 to be small We saw that EDMs at one loop are under control EDMs at two loops? ( Barr-Zee ) 3) PH: Supersymmetry phenomenology - more focused on Flavor and CP problems [Barbieri, Bertuzzo, Farina, PL, Zhuridov, MFV with hierarchical squark masses 2010] [Bertuzzo, Farina, PL, On the QCD corrections to F=2 FCNC in the Supersymmetric SM with hierarchical squark masses 2010] same order as one loop (mass suppr. loop suppr.) With the light part of the spectrum at about 500 GeV, we are on the edge of the EDM experimental bound with large phases Phenomenological consequences: possible signals in B-physics

24 REF: Problem in the original papers: too large FV in Right Handed sector large contrib. to k Solution: 4) PH: consequences of a U(2)^3 flavor symmetry in supersymmetry [Barbieri, Isidori, Jones-Perez, PL, Straub, U(2) and Minimal Flavor Violation in Supersymmetry 2011] Assumption: only weakly broken in a minimal way O("$) Single (2,1,1) ensures MFV-like protection of FCNC

25 REF: 4) PH: consequences of a U(2)^3 flavor symmetry in supersymmetry [Barbieri, Isidori, Jones-Perez, PL, Straub, U(2) and Minimal Flavor Violation in Supersymmetry 2011] Going to the physical basis: Additional FV terms: 1

26 REF: 4) PH: consequences of a U(2)^3 flavor symmetry in supersymmetry [Barbieri, Isidori, Jones-Perez, PL, Straub, U(2) and Minimal Flavor Violation in Supersymmetry 2011] (CKMfitter and UTfit obtain similar results)

27 REF: 4) PH: consequences of a U(2)^3 flavor symmetry in supersymmetry [Barbieri, Isidori, Jones-Perez, PL, Straub, U(2) and Minimal Flavor Violation in Supersymmetry 2011] Leading term: with:, Universal CPV in B-mixing, positive contribution to K Global No more tension CKM fit

28 REF: 4) PH: consequences of a U(2)^3 flavor symmetry in supersymmetry [Barbieri, Isidori, Jones-Perez, PL, Straub, U(2) and Minimal Flavor Violation in Supersymmetry 2011] Gluino and sbottom left masses below TeV S%& above its tiny SM value, but not as much as Generic U(2) model with S%& not correlated to 'k [Ligeti et al 2010]

29 REF: Gauge mediation in two-site model: 4) PH: consequences of a U(2)^3 flavor symmetry in supersymmetry [Barbieri, Isidori, Jones-Perez, PL, Straub, U(2) and Minimal Flavor Violation in Supersymmetry 2011] Link fields we chose: [Craig, Green, Katz, 2011] With nonren. terms: then using simple discrete symmetries one can find exactly what was discussed

30 The Flavor problem in general SM as effective theory: From [Rattazzi, CHIPP2012] Unnatural SM: flavor as in SM (just CKM), B and L conservation Natural SM: flavor not as in SM Higgs not SM-Higgs

31 Natural Supersymmetry 1) Insisting on Naturalness Increased quartic coupling makes hierarchical (and heavier) sfermions more natural. SM-like Higgs mass can then be reduced by mixing, as in [Hall et all ]

32 1b) Escaping the bounds Possibility: keep Naturalness, but escape the bounds A first possible way out: $SUSY with $=2. Stop at 1 TeV can be compatible with "=10 [Hall, talk Oct ]

33 1b) Escaping the bounds R-Parity violation Recall: q.n. of Hd superfield equal to those of left handed lepton doubl. L Baryon and Lepton numbers are not acc. symm. of the theory Way to avoid proton decay: impose R-Parity R=(-1) 3(B-L)+2S LSP is stable DM candidate + missing energy at colliders What if it is (slightly) violated?

34 1b) Escaping the bounds Other possibilities Compressed Spectrum: acceptance of Jet+MET signal is reduced in 'compressed' configurations (e.g small MGluino-MLSP): See e.g. [LeCompte, Martin, , ] Stealth SUSY: Main ingredient: 'stealth' sector with Mparticles ) Msparticles, with 'ordinary LSP' stealth sector true LSP (small phase space). [Fan, Reece, Ruderman, , ]

35 2-3) Only DM and unif., or strings Split and High-scale Susy Retaining (ii)-(iv) Split SUSY [A.-Hamed et al, ] [Giudice et al, ] At low energy only SM particle content plus Higgsinos and gauginos. Many interesting peculiar features [A.-Hamed et al, ] Abandoning (i) Only (iv) High-scale SUSY [Hall,Nomura, ] At low energy only SM, all the rest is decoupled Interesting feature of both: (assuming only MSSM particle content) Higgs boson mass is very precisely determined in terms of the higher scale

36 2-3) Only DM and unif., or strings Consequences: by construction, only from Higgs mass Prediction of SUSY breaking scale from mh < 127 GeV (assuming no additional physics...) Results: Split SUSY: High scale SUSY: [Giudice, Strumia, ] MS < 10^5 TeV No firm conclusion [Arbey et al, ] If chargino and neutralino candidates are found, then must measure couplings and check SUSY relations ([Cheng et al ][Katz et al, ]etc) probably at Linear Collider... For review of the Split-SUSY phenomenol. [A.-Hamed, ]