[Hps] LHCb arXiv:1509.06765

[Natalia Toro]

Hi Valery, all,

Yes, I think their prospects look very exciting and if they hold up will
completely change the landscape below 100 MeV.  One thing worth noting is
the timeline -- as they say, the search relies on Run 3 upgrades and the
full run-3 dataset (currently planned for 2020-2023).

I also don't know whether they have discovery potential in "Mont's gap" or
only exclusion...

Best,
Natalia

On Thu, Sep 24, 2015 at 10:48 AM, Valery Kubarovsky <vpk at jlab.org> wrote:

> LHCb will cover
> LHCb can explore nearly all of the dark photon parameter space between
> existing prompt-$A^{\prime}$ and beam-dump limits for heavy photon mass <
> 100MeV.
>
>
> [2]  arXiv:1509.06765 [pdf, other]
> Dark photons from charm mesons at LHCb
> Philip Ilten, Jesse Thaler, Mike Williams, Wei Xue
> Comments: 18 pages, 11 figures, 1 table
> Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy
> Physics - Experiment (hep-ex)
> We propose a search for dark photons $A^{\prime}$ at the LHCb experiment
> using the charm meson decay $D^*(2007)^0 \!\to D^0 A^{\prime}$. At nominal
> luminosity, $D^{*0} \!\to D^0 \gamma$ decays will be produced at about
> 700kHz within the LHCb acceptance, yielding over 5 trillion such decays
> during Run 3 of the LHC. Replacing the photon with a kinetically-mixed dark
> photon, LHCb is then sensitive to dark photons that decay as
> $A^{\prime}\!\to e^+e^-$. We pursue two search strategies in this paper.
> The displaced strategy takes advantage of the large Lorentz boost of the
> dark photon and the excellent vertex resolution of LHCb, yielding a nearly
> background-free search when the $A^{\prime}$ decay vertex is significantly
> displaced from the proton-proton primary vertex. The resonant strategy
> takes advantage of the large event rate for $D^{*0} \!\to D^0 A^{\prime}$
> and the excellent invariant mass resolution of LHCb, yielding a
> background-limited search that nevertheless covers a sig!
>  nificant portion of the $A^{\prime}$ parameter space. Both search
> strategies rely on the planned upgrade to a triggerless-readout system at
> LHCb in Run 3, which will permit identification of low-momentum
> electron-positron pairs online during data taking. For dark photon masses
> below about 100MeV, LHCb can explore nearly all of the dark photon
> parameter space between existing prompt-$A^{\prime}$ and beam-dump limits.
>
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-- 
Natalia Toro
Perimeter Institute
31 Caroline St N, Waterloo, ON
(519) 569-7600 x8725
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