Author:
Fox Patrick J.,Jindariani Sergo,Shiltsev Vladimir
Abstract
Abstract
While dimuonium (μ
+
μ
-) — the “smallest QED atom”
— has not yet been observed, it is of utmost fundamental interest.
By virtue of the larger mass, dimuonium has greater sensitivity to
beyond the standard model (BSM) effects than its cousins positronium
or muonium, both discovered long ago, while not suffering from large
QCD uncertainties. Dimuonium atoms can be created in e
+
e
-
collisions with large longitudinal momentum, allowing them to decay
a small distance away from the beam crossing point and avoid prompt
backgrounds. We envision a unique cost-effective and fast-timeline
opportunity for copious production of (μ
+
μ
-) atoms at the
production threshold via a modest modification of existing Fermilab
Accelerator Science and Technology (FAST) facility to arrange
collisions of 408 MeV electrons and positrons at a 75°
angle. This compact 23 m circumference collider (DIMUS) will allow
for precision tests of QED and open the door for searches for new
physics coupled to the muon. The FAST facility is perfectly suited
for DIMUS as there are existing SRF accelerators and infrastructure,
capable of producing high energy, high current electron and positron
beams, sufficient for O(1032)cm2 s-1
luminosity and ∼0.5 million dimuons per year. The expansion
will require installation of a second SRF cryomodule, positron
production and accumulation system, fast injection/extraction
kickers and two small circumference intersecting rings. An
approximately meter-sized detector with several layers of modern
pixelated silicon detector and crystal-based electromagnetic
calorimeters will ensure observation of the decays of dimuonium to
electron-positron pairs in presence of the Bhabba scattering
background. An expansion of the system to include solenoidal magnet
outside of the calorimeter system, a layer of steel shielding behind
the magnet, and a set of dedicated muon detectors would extend the
physics program of DIMUS to include precision studies of rare
processes with muons, pions, and η mesons produced in
e
+
e
- collisions.
Subject
Mathematical Physics,Instrumentation