Les Houches

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Responsibles: Grégory Moreau [TH](moreau@th.u-psud.fr), Jose Miguel No [TH] (josemiguel.no@uam.es), Susan Gascon-Shotkin [EXP](smgascon@mail.cern.ch)

People involved (TBC!!): Sophie Williamson (swilliamson@lpthe.jussieu.fr), Aoife Bharucha (aoife.bharucha@cpt.univ-mrs.fr), Antoine Lesauvage (antoine.baptiste.lesauvage@cern.ch), Jérémie Quevillon (jeremie.quevillon@lpsc.in2p3.fr), Shilpi Jain(shilpi.jain@cern.ch), Shankha Banerjee (banerjeeshankha@gmail.com), Biplob Bhattacherjee(bbhattacherjee@gmail.com), Nishita Desai (nishita.desai@umontpellier.fr), Jon Butterworth (J.Butterworth@ucl.ac.uk), Natascia Vignaroli (vignaroli@pd.infn.it), Kohsaku Tobioka (ktobioka@fsu.edu), José Zurita (jose.zurita@kit.edu), Giacomo Polesello (giacomo.polesello@cern.ch). 

Please add your initials to sub-projects!

**Exotic Higgs decays into h -> Z $\phi$** (see also discussion in [[2019:groups:higgs:seminvisible|]]). 

Reference to look for general motivation on exotic Higgs decays, possible models, etc, as well as for information on theoretical work and experimental analylis (as of 2013!): Review/compendium work on exotic Higgs decays from Curtin, Gori, Shelton, Strassler et al [[https://arxiv.org/abs/1312.4992|1312.4992]]. 

We consider two decay modes of $\phi$: $\phi \to \gamma \gamma$, $\phi \to \mu \mu$ 

  * $\phi$ -> $\gamma\gamma$. (**SG,AL**)

Preliminary study from Bauer, Neubert, Thamm [[https://arxiv.org/abs/1708.00443|1708.00443]] (see also [[https://arxiv.org/pdf/1704.08207.pdf|1704.08207]]).  

For m_{\phi} < 47 MeV, constraints from $h \to Z \gamma$, since for m_{\phi} < 47 MeV the two photons from the $\phi$ decay are very collimated and seen as one in the detector.

For m_{\phi} > 47 MeV, they compute just number of signal events for $gg \to h \to Z \phi$, and assume limits for 100 events at LHC. 

$m_\phi < 35$ GeV: $h \to Z \phi$ (on-shell $Z \to \ell\ell$)

$m_\phi > 35$ GeV: $h \to Z^* \phi$ ($h \to \ell\ell \phi$)

__TO DO LIST__ 

  - ASK FOR FEYNRULES FILE! 
  - Validate UFO File {{ :2019:groups:higgs:alp-pr.tar.gz |ALP UFO file }} (fixed by Peter Richardson) from Bauer, Thamm, Neubert. **[JN, SW]** //NOTE: We need to check for effective ggh coupling in UFO.// (CHECKED: They Have it, so we can generate gluon fusion production of $h$)
  - SM background generation. **Done** **[SG,AL]**
  - Generate signal: study kinematics of different $h$ production modes, as well as $m_{\phi}$ dependence.**[SG,AL]**
  - Contur study (related to next item). Give **JB** range of parameters to scan for the model. 
  - Other constraints. 1) Higgs signal strengths bound on partial BSM width **[JN, SW]** 2) LEP Z width: Z → $h^*$ $\phi$, $h^*\to bb...$ leads to constraints from Z total width. **[JN, SW]** 3) LEP Exclusive Z decays? 4)...
 
  * $\phi$ -> $\mu\mu$ Possiblly useful refs ($h\to ZZ^*\to4\mu$[[https://cds.cern.ch/record/2621479/files/ATLAS-CONF-2018-018.pdf| ATLAS-CONF-2018-018]],[[https://cds.cern.ch/record/2668684/files/HIG-19-001-pas.pdf|CMS]]; $h\to aa\to4\mu$[[https://arxiv.org/abs/1812.00380|1812.00380]]; $h\to aa\to2\tau2\mu$ [[https://inspirehep.net/record/1419565/files/HIG-15-011-pas.pdf|HIG-15-011-pas]], [[https://arxiv.org/pdf/1505.01609.pdf|1505.01609]]; $h\to ZZ_d\to 4l$[[http://arxiv.org/abs/1802.03388|1802.03388]])

Similar strategy to the one above!  In principle above 10 GeV we are safe from SM low mass resonances. Below 10 GeV? Also, how low can one go in mass by playing with muon isolation.

$h \to Z \phi$, $Z \to \mu\mu$, $\phi \to \mu\mu$ recasted from existing analysis of $h \to \phi \phi$, $\phi \to \mu\mu$.
Les Houches

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