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SUMMARY:Searching for Dark Photons and the X17 Anomaly with the Upgraded L
 HCb Detector
DTSTART:20261008T140000Z
DTEND:20261008T150000Z
DTSTAMP:20261005T003500Z
UID:indico-event-5016@indico.e5.physik.tu-dortmund.de
CONTACT:mick.mulder@tu-dortmund.de\;lukas.witola@tu-dortmund.de
DESCRIPTION:Speakers: Carlos Cocha Toapaxi (Universität Heidelberg)\n\nTh
 e search for new light and weakly coupled particles provides a promising a
 venue to probe physics beyond the Standard Model and to explore possible c
 onnections to the dark matter sector. In this seminar\, I will present the
  first search for dark photons below the dimuon threshold at the LHC\, usi
 ng radiative charm decays collected with the upgraded LHCb detector during
  Run 3. The search targets the decay $A' \\to e^+e^-$ in processes such as
  $D^{*} \\to D A'$\, exploiting the large charm production rate and the up
 graded detector capabilities to probe a region of dark photon parameter sp
 ace that remains largely unexplored at LHC experiments. The accessible mas
 s range includes the region relevant to the $m(e^+e^-)\\approx17$ MeV/$c^2
 $ (X17) anomaly reported by the ATOMKI experiment. In particular\, radiati
 ve $D_s^{+}(c\\bar{s})$ decays provide sensitivity to scenarios in which t
 he hypothetical X17 boson couples to both first- and second-generation qua
 rks\, allowing models with universal quark couplings to be tested. I will 
 present the first results obtained with a subset of the Run 3 dataset and 
 discuss the resulting sensitivity to prompt-like dark photon models and X1
 7-motivated scenarios.Finally\, I will briefly discuss the development of 
 a novel inclusive trigger selection targeting photons converting to $e^+e^
 -$ pairs downstream of the Vertex Locator subdetector. This trigger extend
 s the real-time reconstruction capabilities of LHCb for converted photons 
 and displaced topologies\, providing an additional tool for analyses invol
 ving photons. Downstream converted photons offer excellent photon-energy r
 esolution at LHCb\, as they are less affected by upstream material effects
  and their energy and direction can be reconstructed from the electron tra
 cks and conversion vertex rather than relying solely on calorimetric photo
 n reconstruction. This is particularly valuable for soft photons\, where c
 alorimetric reconstruction can be challenging\, and can significantly impr
 ove the invariant-mass resolution in radiative decay modes. Simulation stu
 dies indicate substantial improvements in the mass resolution for several 
 key radiative decays of interest at LHCb\, highlighting the potential of t
 his approach for both long-lived-particle searches and precision measureme
 nts involving photons.\n \n\nhttps://indico.e5.physik.tu-dortmund.de/even
 t/5016/
LOCATION:CP-03-123 - E5a Seminarraum (TUDortmund)
URL:https://indico.e5.physik.tu-dortmund.de/event/5016/
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