Models as existence proofs, speculations or... peaces of physical reality

Transcription

1 Models as existence proofs, speculations or... peaces of physical reality Riccardo Barbieri Zuoz II, July 16/21, 2006 An example of what could happen, based on: An ultra-bottom-up hypothesis 2 concrete realizations (why not a single one?)

2 The idea RB, Hall Seek simple Higgs sector that: 1. Agrees with all data (EWPT) 2. Is fully natural up to 1.5 TeV ( + maybe something else) A modest ultra-bottom-up approach, with crucial consequences for LHC

3 A Heavy SM Higgs and the EWPT T IDM = T SM +!T S IDM = S SM +!S A heavy Higgs m h = GeV + a positive ΔT Origin of ΔT?? (Peskin, Wells and many others) prefer models that populate the 1-2σ ellipse in most of parameter space. Are there any?

4 2 HDM in an alternative phase RB, Hall, Rychkov IDM controlled by approximate SU(2) V

5 The IDM is natural and perturbative up to ~1.5 TeV (instead of the SM only up to ~ 400 GeV) H NL L with and m h = GeV ] m H m NL ]!m mh mnl and an average mass m av (m L,m NL,m H ) 100 GeV 1 TeV m

6 A Dark Matter candidate Unbroken H 2 H 2 Inert scalars always in pair (for natural flavour conservation) Stable lightest inert scalar To get the observed! m need co-annihilation of S, A into light fermions as dominant process m GeV m L GeV Shouldn t one have seen S and A at LEP2 via e + e A + S (Z + S) + S What about direct DM detection! h (Lp Lp) pb ( "L 0.5? ) 2 ( ) 2 ( 70GeV 500GeV m L? m h ) 4

7 Can one do better than! nat 1.5 TeV? 2H doublets Supersymmetry ( UV completion )... but without a light Higgs boson! How?? In the most straightforward way: Add a coupling λ through! f = "SH 1 H 2 with λ only constrained by perturbativity up to TeV λsusy NMSSM with! low energy 2 dominating over all other couplings RB, Hall, Nomura, Rychkov Not consistent with gauge unification? An open question, depending on the physics above TeV See, e.g., Harnik et al, Gripaios and West

8 ElectroWeak Precision Tests in λsusy S and T from Higgs s M( S)! = 2 S and T from Higgsinos tan! 2.5 m( H ± ) For and s-particles in their natural range, most of parameter space inside the 1-2σ ellipse tan! = 1 an exact custodial symmetry point

9 Particle spectrum (naturalness bounds) in λsusy! = 2 with up to 20% tuning (m max! "/5) and no significant bound on other s-fermions and SU(2)xU(1) gauginos! mess = 100 TeV

10 Dark Matter in λsusy blue:!h 2 = white:!h 2 < 0.09 red:!h 2 > 0.13 grey: m LSP < 45 GeV black lines: m LSP = m W,m Z LSP =! S + " H 1 + # H 2 with no special relation among parameters (MSSM)

11 Provisional conclusions Doubling the Higgs multiplet the simplest solution (?) of the l.h.p., realized in several possible ways 1 TeV H ±,A,H 500 GeV h + possibly something else Relevant to supersymmetry itself? LHC will explore for the first time the relevant energy range, well above the Fermi scale

12 An example: The Inert Doublet Model Consider the most general 2H doublet model invariant under H 2 H 2 to get natural flavour conservation (i.e., only couples to matter) +! 4 H 1 H 2 2 +! 5 2 [(H 1 H 2) 2 + h.c.] H 1 RB, Hall, Rychkov V = µ 2 1 H µ 2 2 H 2 2 +! 1 H 1 4 +! 2 H 2 4 +! 3 H 1 2 H 2 2! 4,! 5 custodial symmetry! 5 PQ symmetry Take µ 2 1 < 0, µ 2 2 > 0 so that H 1 = ( φ + v + (h + iχ)/ 2 ), H 2 = ( H + (S + ia)/ 2 )

13 The Inert Doublet Model (continued) Parameter space: µ 2 1,! 1 v(m Z ), m h! 2 (in the usual way) (not relevant to the spectrum) µ 2 2,! 3,4,5 m L,m NL,m H ;! L m 2 H = µ 2 2 +! 3 v 2 m 2 S = µ (! 3 +! 4 +! 5 )v 2 m 2 A = µ (! 3 +! 4! 5 )v 2! L! 3 +! 4! 5 custodial symm. limit: PQ symmetry limit: m H = m S = m A m S = m A absolute minimum:! 1,2 > 0! 3,! L! 3 +! 4! 5 > 2(! 1! 2 ) 1/2

14 Naturalness, perturbativity, EWPT in the IDM!m 2 h = " t # t 2 + " g # 2 g + " 11 # 2 H 1 + " 12 # 2 H 2!µ 2 2 = 1 ( "g # 2 g + " 22 # 2 H " 21 # 2 ) H 1 16! 2 d" i d log# = $ i(")! nat = min(! i ) 1.5 TeV

15 T IDM = T SM +!T SIDM = S SM +!S!S!T negligible 1 24" 2 #v 2(m H m A )(m H m S ) In the Standard Model: m h = GeV In the IDM: m h = GeV (m H m S )(m H m A ) = M 2, M = GeV

16 Collider Signals 1. m h = GeV A standard Higgs boson? h SS,AA,H + H at! h = 68 GeV m h = 500 GeV 2. pp W HA or HS H AW or SW A SZ ( ) for the DM parameters, looking for 3 charged leptons! signal 3.5 fb! bg 20 fb