CMS ütközés
High Energy Experimental Particle and Heavy Ion Physics

Group leader: Veszprémi Viktor


Physics analyses and theoretical work. — Our group has measured cross-section limits on
supersymmetric processes leading to strongly boosted top quark decays in the data
recorded by the CMS detector at the LHC prior to the 2017 installation of the new pixel
detector. We have also doubled the recorded collision data using the new pixel detector
during 2017. We provided a member for the Publication Committee of the CMS Experiment
at CERN and played an important role in publishing CMS results of low-x QCD studies.
The group participated in the ASACUSA experiment at the Antimatter Factory of CERN,
which provides a test of the CPT invariance, the theorem stating the equivalence of matter
and antimatter, via measuring the transition energies of antiprotons trapped helium atoms
using laser spectroscopy. The method leading to the precise determination of the
agreement between the proton and antiproton masses earlier was extended to superfluid
helium; the data are still in analysis. The first steps were made to use two-photon laser
spectroscopy on antiprotonic helium atoms cooled down below 1.7 K in cryogenic lowpressure
helium gas.

We wrote and published the first Hungarian textbook of quantum information theory. We
proposed the Principle of Least Decoherence and, based on it, improved the widely used
theory of semi-classical gravity, which will henceforth not violate the linearity of quantum

Work on instrumentation. — The group has successfully commissioned the new pixel
detector installed at the CMS experiment in 2017, the control and read-out electronics of
which device was developed and manufactured by our group. We have prepared the 3D
detector model and the software for the reconstruction of the new data, organized the
spatial and temporal alignment of the new detector, and completed the calibration of the
reconstruction algorithms. We also verified that the detector performance meets its design

The stable operation of the T2_HU_Budapest grid site continued in 2017. Our site is used
extensively by the entire CMS collaboration including our group for reconstructing collision
data in physics analyses. The disk capacity committed to CMS has increased to 900 TB.
We have successfully tested two superconducting shield prototypes for the Superconducting
Shield Septum project: a high-temperature superconductor and MgB2. The performance of
the MgB2 prototype was satisfactory for its application. We have designed and constructed
a device called “SPS Diffuser”, which will be installed in the CERN SPS accelerator to
decrease the radiation load on the electrostatic septum.
Outreach. – Two education programs were organized by Wigner RCP at CERN with the
leadership of our group: the High-School Student Internship Programme (22 May - 2 June
2017) with the participation of 22 students and the Hungarian Teachers Programme (15-21
August 2016) for 21 physics teachers. For the teachers we organized a meeting on
November 25 at Wigner RCP in the presence of representatives of the Hungarian Physical
Society, the Hungarian CERN Committee and the main sponsor, the Pallas Sthene Domus
Innovationis Foundation. We also participated in the organization of the annual Hands-on
Particle Physics Master-classes on two occasions with 22 high-school students attending
each session. In addition to conference talks and university teaching, many popular lectures
were given by our group.