Les Houches

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PAIRED RESONANCES

• People involved: Giacomo, Aldo, Lorenzo, Guillarme, Sasha B… (please insert your name if interested to join)

The main idea is to study in a (possibly) model independent way scalar and vector resonances that are easier to constraint when pair-produced than when singly produced, and that then decay into pairs of SM states. The typical final state will therefore be a pair of resonances. We will list all possible allowed states and construct simplified models to describe them, giving where possible references to existing models as example of their realisation.

Considered resonances can be spin-0 (scalar) or spin-1 (vector), coloured or SU(3)-singlet, and a fairly simple classification can be done accordingly to their transformation under the SU(2)_L × U(1)_Y group of the SM. Fermionic resonances (such as vector-like quarks or leptons) are already considered elsewhere.

The main idea behind this, is that low-mass resonances decaying into jets are loosely constrained for masses below (roughly) 1 TeV, leaving open quite some space for relatively light states (compatible with Tevatron limits).

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Parameterisation

1. Uncoloured resonances

We start with singlets of SU(3)_C that are easier to describe. According to SU(2)_L × U(1)_Y, we can have

• Vector SU(2) Singlets S_\mu ~ (1,Y)

In order to couple to pairs of SM fermions, Y=0,±1. The case Y=0 is uninteresting here, because it has only trivial gauge couplings (still it can be considered in VLQ decays). Hence, the only possibility is Y=±1, leading to a vector with charge ±1 (singlet W').

The only vector current that can be written that preserves Lepton and Barion number couples the vector to RH quarks: g_S \bar{u}_R S_\mu \gamma^\mu d_R

Single production is model dependent and depends on g_S. It usually dominates over pair production, which might take over for small g_S values. On the other side, pair production is mediated by SM gauge interaction and from this point of view, it is rather model independent.

Signatures: jjjj (covered), tbjj (interesting), tbtb (hopeless?)

Exemple reference: […]

• Scalar SU(2) Singlets S ~ (1,Y)

To be filled

• Vector SU(2) Doublets D_\mu ~ (2,Y)

Perhaps the most interesting case.

• Scalar SU(2) Doublets D ~ (2,Y)

To be filled