Daniel Spitzbart

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Particle Physicist
Boston, MA

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About me

I’m a particle physicist currently working at Boston University. I work with the CMS experiment at the CERN Large Hadron Collider. I was a LPC Distinguished Researcher for the 2022 and 2023 terms at the Fermi National Accelerator Lab LHC Physics Center. My github username is inspired by Bart Simpson’s alter-ego El Barto.

I like running or riding my bike around Boston, reading books and listening to good music.

Research interests

My research is currently focussed on understanding the coupling of top quarks to the SM gauge bosons. You can find results of my previous work in this paper, and projections for future results in this document. A large part of my research work currently revolves around the development of a new part of the CMS detector that can measure the arrival time of particles with a below 40ps time resolution..

During my PhD thesis I focussed on searches for supersymmetric particles like gluinos or top squarks.

Projects

Development of a precision particle timing detector

Upgrades to the Large Hadron Collider will increase the number of simultaneous proton collisions by a factor of 4. This will help physicists record more interesting events to analyze, but will introduce challenges to disentangle collision vertices from different protons within the same bunch crossing. While vertices will overlap in space too close to be distinguished using spatial information alone, the collisions are spread enough in time that a detector with 30ps time resolution will be able to separate them. The initial design of such a new detector is described in the CMS Technical Design Report No 20. I have worked on the design and layout of the detector that will be installed in the endcaps of the CMS experiment, and have developed front-end electronics, back-end firmware as well as control and analysis software together with engineers and students at Boston University. A prototype detector has recently been successfully tested in an electron/positron beam at the DESY II test beam facility in Hamburg, Germany. In the future, such detectors will enable full 4D tracking and will be paramount to experiments at upcoming particle collider experiments.

Searches for Supersymmetry

Supersymmetry is one of the most appealing theories to solve several shortcomings of the Standard Model of particle physics (SM). One of the main predictions is the introduction of partner particles to the SM particles, which differ in mass and spin, and are usually named simlar to SM particles with a -ino suffix or a s- prefix I have worked on and lead searches for the production of gluinos, top squarks and electroweakinos. Innovative strategies and statistical combinations of these efforts have lead to some of the most stringent constraints on the tested models to date. I have also developed a new algorithm to improve discrimination against transverse momentum imbalance from resolution effects, the MET significance, based on bootstrap methods. The traditional version of this algorithm has been used in searches for top squarks. Reinterpretations of the results also tightly constrain some models for Dark Matter production and the invisible decays of Higgs bosons.

Measurements of top quark couplings

Couplings of the top quark to SM bosons are subject to corrections from massive particles beyond the SM, leading to subtle changes in the production rate and particle spectra of rare SM processes. I have developed new analyses that measure the coupling of the top quark to the Z boson. In a first attempt to precisely measure spectra of the Z boson we were able to confirm the SM predictions with unprecedented precision. A complementary method of confirming these measurements is currently in development. Many theories, for example ones that include an extended Higgs sector, predict flavor-changing neutral currents which are highly suppressed in the SM. Results that we obtained set some of the most stringent limits on these models.

Collimation System for a High-Power Proton-Synchrotron

High-intensity neutrino beams can be created by directing the proton beam from a high-power proton accelerator into a fixed target. A new high-power proton-synchrotron has been studied at CERN, delivering a 2 MW beam that is steared using superconducting magnets. Particle losses into the aperture of the accelerator have to be minimized to avoid quenching of the superconducting magnets. Beam-halo particles therefore have to be cleaned away using a well crafted collimation system. I have simulated and optimized the material, thickness and position of a collimation system that aims to achieve losses of less than 1 W/m.

Development of test benches and control valves

As a R&D engineer I have developed several new testing methods and designed test benches to characterize and improve quality control for high-precision control valves. I have coordinated work with different companies to adopt servo drives as actuators for improved control precision and speed.

Honors

Selected publications

Search for top squark pair production in dilepton final states, 2020

Measurement of top quark pair production in association with a Z boson in proton-proton collisions at 13 TeV, 2019

Standard Model Physics at the HL-LHC and HE-LHC, 2019

Performance of missing transverse momentum reconstruction in proton-proton collisions at 13 TeV using the CMS detector, 2019

First constraints on invisible Higgs boson decays using ttH production at 13 TeV, 2019

Search for top squarks and dark matter particles in opposite-charge dilepton final states, 2017, Proceedings

Search for supersymmetry in events with one lepton and multiple jets exploiting the angular correlation between the lepton and the missing transverse momentum in proton-proton collisions at 13 TeV, 2017

Selected talks

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