  The LHC program will include the identification of events with single prompt
high-k_\perp photons as probes of new physics. We show that this channel is
uniquely suited to search for experimental evidence of TeV-scale open string
theory. At the parton level, we analyze single photon production in gluon
fusion, gg \to \gamma g, with open string states propagating in intermediate
channels. If the photon mixes with the gauge boson of the baryon number, which
is a common feature of D-brane quivers, the amplitude appears already at the
string disk level. It is completely determined by the mixing parameter (which
is actually determined in the minimal theory) -- and it is otherwise
model-(compactification-) independent. We discuss the string signal cross
sections as well as the QCD background. The present analysis takes into account
the recently obtained decay widths of first Regge recurrences, which are
necessary for more precise determination of these cross sections in the
resonant region. A vital part of the background discussion concerns the
minimization of misidentified \pi^0's emerging from high-p_\perp jets. We show
that even for relatively small mixing, 100 fb^-1 of LHC data could probe
deviations from standard model physics associated with TeV-scale strings at a
5\sigma significance, for M_{\rm string} as large as 2.3 TeV. It is also likely
that resonant bumps could be observed with approximately the same
signal-to-noise ratio.
