Les Houches
2017 Session

 Working Groups & Topics
Wikis of Previous sessions
Les Houches Themes
(Lyrics and Music)
(Lyrics and Music)
Interested people: Jose Miguel No, Jose Zurita, Stefania Gori, Ken Mimasu, Linda Finco, Sijing Zhang, Susan GasconShotkin, Grégory Moreau, Haiying Cai, Sylvain Fichet, Thomas Flacke, Stefan Liebler, Daniele Barducci, Andrei Angelescu, Jon Butterworth
Down to which masses the LHC can test (pseudo)scalars?
Below 8090GeV, for a generic (pseudo)scalar $\phi$ (light Higgs, radion, dilaton, axion,…), the decay $\phi$ → Z*Z is kinematically closed and $\phi$ → $\gamma\gamma$ becomes challenging to trigger on, so that the gluongluon Fusion mechanism to produce $\phi$ is not promising anymore (see for instance 1607.08653).
1. Associated production ($pp \to V \phi$) [contact: Grégory Moreau]
Motivation: the produced Vector boson V helps to trigger on the signal (for example: Radion+Z production within the RS model studied in 1702.03984).
Context here: EFT with onshell scalar ($\phi$) and scalar couplings to vector bosons only so look at the decay $\phi \to \gamma \gamma$ [here $\phi$ is not a stable DM candidate leading to missing $E_T$]. Looking at scalar couplings to fermions, other production and decay modes ($\phi \to \tau \tau$ or $\phi \to b \bar b$ [reconstructing the invariant scalar mass]) could be studied as well.
Gauge invariant (pseudo)scalar couplings to ZZ, WW, $\gamma\gamma$, $\gamma$Z, gluongluon: $$\frac{\phi}{f_H}\vert D_\mu H\vert^2 \ , \ \ \frac{\phi}{f_Z} Tr[V_{\mu\nu} V^{\mu\nu}] \ \ and \ \ \frac{\phi}{\tilde f_Z} Tr[V_{\mu\nu} \tilde V^{\mu\nu}] \ .$$
Two other effective parameters: $\phi$ mass ($m_\phi$) and Branching for $\phi \to \gamma \gamma$ ($B_\gamma$).
Exhaustive list of hard processes (no focus on W production for EXP reasons):
A first work Plan: (1) implement the effective model into FeynRules (2) produce kinematical distributions for the signal with MadGRAPH (directly from the LHE files with madAnalysis for example) (3) interface the DELPHES detector response simulator (at the MadGRAPH level) (4) compare distributions for SMlike couplings ($1/f_H$) and kineticlike couplings ($1/f_Z$, $1/\tilde f_Z$) [also to develop a discrimination test between e.g. a light Higgs and a radion] (5) simulate SM background events as well (main physical one: DrellYan + double ISR/FSR ?) (6) optimise a set of selection cuts (7) obtain a sensitivity plot (prospective for Run 2) in the parameter space: $m_\phi$, $1/f_H$, $1/f_Z$, $1/\tilde f_Z$ [=couplings for the considered gauge bosons] for $B_\gamma$=100% (plot to be simply rescaled accordingly to the wanted $B_\gamma$ value then). (+motivate EXP analysis of exclusion limits from Run 1 data?).
Goal: derive a generic plot that can be recast to any specific theoretical scenario with a light (pseudo)scalar, and, determine its complementarity with LEP(,EWPT) bounds.
Tools: Some of us are looking at this using Contur.
2. Complementarity with “single” scalar production [same context / strategy as in point 1.]
For example, motivated in extended Higgs sectors (e.g. light Higgses in 2HDM) when the 125GeV is SM like (2HDM “alignment limit”).
3. Exotic Higgs decays: What are the holes? [contact: Stefania Gori, Jose Miguel No]
h → a a, Z a, a a' with a, a' scalar/pseudoscalar (for Z a, a is pseudoscalar)
h→chi1 chi2
Exotic Higgs decays into LLP (displaced vertices). Role of LHCb (also BaBar, Belle II)