HyperchargeUniversal Topcolor PHENO 2008 Stefano Di Chiara HyperchargeUniversal

Hypercharge-Universal Topcolor PHENO 2008 Stefano Di Chiara

Hypercharge-Universal Topcolor The model is a topcolor-assisted technicolor (TC 2): • mass of leptons and light quarks given by extended technicolor sector (ETC) • mass of the top quark generated mostly by extended color sector • mass of the Z and W bosons given by a top quark condensate and a technifermion condensate. Assume part of the ETC group breaks down to the TC group, generating contact interactions between technifermions and fermions. The resulting gauge group, with relative couplings, of the model is Braam, Flossdorf, Chivukula, Di Chiara, Simmons: 0711. 1127 Stefano Di Chiara PHENO 2008 1

Gauge Charges Gauge charge assigments for the SM fermions chosen to allow condensation of the top quark alone: • • h 1 > h 2 to allow condensation only in the III generation U(1)1 charges to tilt the vacuum toward the top quark The mass of the top can be large without important FCNC. Stefano Di Chiara PHENO 2008 2

Gauge Charges Alternative assigments define the classic and the flavor-universal TC 2: Hill: hep-ph/9411426 Popovic, Simmons: hep-ph/9806287 Stefano Di Chiara PHENO 2008 3

Symmetry Breakings Symmetry-breaking sequence of the model: A condensate, with charges topcolor group at the scale u. breaks the Both the top and the technifermions condensates contribute to the electroweak symmetry breaking scale v. Stefano Di Chiara PHENO 2008 4

Top Condensate Conditions to generate condensate from the gap equation: inside the triangular region only the top condenses. In region: (i) bottom condenses (ii) tau condenses (iii) top condenses mt=172 Ge. V for u >500 Ge. V solutions lie on the left of dashed line. Stefano Di Chiara PHENO 2008 5

Spectrum & Parameters Techni-fermions and top quark condense respectively at energies: The particles present in the model are: • SM fermions and gauge bosons • triplet of massive top-pions • coloron (massive top-gluon), Z` boson • massive techni-fermions, techni-gluons The undetermined (but experimentally constrained) parameters are: Stefano Di Chiara PHENO 2008 6

EW Masses & Couplings The electroweak boson masses are: and the relative couplings: Stefano Di Chiara PHENO 2008 7

EW Parameters A parametrization of the corrections to the SM tree level EW neutral and charged current amplitudes is given by: S = measure of the size of electroweak sector. Chivukula, Simmons, He, Kurachi, Tanabashi: hep-ph/0408262 Stefano Di Chiara PHENO 2008 8

EW Parameters Starting from the amplitudes, the observables have been parametrized as The expressions for in function of the model’s parameters are: Also the weak mixing angle gets a correction: Stefano Di Chiara PHENO 2008 9

Goodness of Fit Hypercharge-Universal TC 2 Stefano Di Chiara PHENO 2008 10

Goodness of Fit The fit with a Higgs reference mass of 800 Ge. V gives corresponding to a 3. 7% probability, This imposes 18 Te. V MC 25 Te. V. This results should be compared to the SM fit with a Higgs mass of 115 Ge. V: corresponding to a 3. 5% probability. Stefano Di Chiara PHENO 2008 11

Allowed Parameter Space The corresponding calculation in different variables gives a 95% C. L. lower bound on the mass of the heavier Z state solid (dashed) line for MH=800 Ge. V (1500 Ge. V): Stefano Di Chiara PHENO 2008 12

Goodness of Fit Flavor-Universal (Classic) TC 2 Stefano Di Chiara PHENO 2008 13

Goodness of Fit The fit with a Higgs reference mass of 800 Ge. V gives corresponding to a 10 -8 probability. Stefano Di Chiara PHENO 2008 14

Conclusions • The Hypercharge-Universal Topcolor model satisfies FCNC and precision EW constraints at the same level of the SM • The best value of the parameters lies at the border of the allowed region (fine tuning) • The Coloron mass is around 20 Te. V: too heavy for possible discovery at LHC • The Z` can be as light as 2. 08 Te. V, within reach for LHC Stefano Di Chiara PHENO 2008 15

Model Parameters Alternatively Coloron and Stefano Di Chiara masses: PHENO 2008