Lawrence R. Sulak
· Professor (David M. Myers Distinguished Professor)Boston University · Physics
Active 1974–2023
About
Lawrence R. Sulak is the David M. Myers Distinguished Professor of Physics at Boston University. His research focuses on the unification of particles and forces of nature using novel calorimetric detectors. He designed and built the first massive liquid scintillator calorimeter and large area drift chambers, and performed the analysis that discovered neutral weak currents using neutrino beams in 1974, demonstrating that the weak and electromagnetic forces are unified. Sulak also designed and prototyped a Cherenkov detector to search for proton decay and neutrino oscillations, leading to the discovery of neutrino oscillations. Applying Cherenkov detection techniques to quartz fibers, he and his collaborators developed the forward calorimeter for the CMS detector at the Large Hadron Collider, which was instrumental in the discovery of the Higgs boson. Throughout his career, Sulak has contributed significantly to neutrino physics, including the first observation of ν-nucleon elastic scattering, evidence for a unified electroweak force, and the detection of neutrinos from supernovae. He has been involved in building multiple large-scale detectors worldwide to study neutrinos from various sources, and has received numerous awards such as the Panofsky Prize, the APS Instrumentation Award, the Rossi Prize, and the Physics Breakthrough Prize in Fundamental Physics. Sulak studied CP violation under renowned physicists and has held faculty positions at Boston University, where he also established a unique internship program at CERN for junior physics majors.
Research topics
- Nuclear physics
- Physics
- Particle physics
- Computer Science
- Quantum mechanics
Selected publications
Journal of High Energy Physics · 2020 · 68 citations
- Physics
- Particle physics
- Nuclear physics
A bstract A search for direct top squark pair production is presented. The search is based on proton-proton collision data at a center-of-mass energy of 13 TeV recorded by the CMS experiment at the LHC during 2016, 2017, and 2018, corresponding to an integrated luminosity of 137 fb −1 . The search is carried out using events with a single isolated electron or muon, multiple jets, and large transverse momentum imbalance. The observed data are consistent with the expectations from standard model processes. Exclusions are set in the context of simplified top squark pair production models. Depending on the model, exclusion limits at 95% confidence level for top squark masses up to 1.2 TeV are set for a massless lightest supersymmetric particle, assumed to be the neutralino. For models with top squark masses of 1 TeV, neutralino masses up to 600 GeV are excluded.
The European Physical Journal C · 2020 · 92 citations
- Physics
- Particle physics
- Nuclear physics
Abstract Normalised multi-differential cross sections for top quark pair ( $$\hbox {t}{\bar{\hbox {t}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mtext>t</mml:mtext><mml:mover><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow><mml:mrow><mml:mo>¯</mml:mo></mml:mrow></mml:mover></mml:mrow></mml:math> ) production are measured in proton-proton collisions at a centre-of-mass energy of 13 $$\,{\text {TeV}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mspace/><mml:mtext>TeV</mml:mtext></mml:mrow></mml:math> using events containing two oppositely charged leptons. The analysed data were recorded with the CMS detector in 2016 and correspond to an integrated luminosity of $$35.9{\,{\text {fb}}^{-1}} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>35.9</mml:mn><mml:mrow><mml:mspace/><mml:msup><mml:mrow><mml:mtext>fb</mml:mtext></mml:mrow><mml:mrow><mml:mo>-</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:mrow></mml:math> . The double-differential $$\hbox {t}{\bar{\hbox {t}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mtext>t</mml:mtext><mml:mover><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow><mml:mrow><mml:mo>¯</mml:mo></mml:mrow></mml:mover></mml:mrow></mml:math> cross section is measured as a function of the kinematic properties of the top quark and of the $$\hbox {t}{\bar{\hbox {t}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mtext>t</mml:mtext><mml:mover><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow><mml:mrow><mml:mo>¯</mml:mo></mml:mrow></mml:mover></mml:mrow></mml:math> system at parton level in the full phase space. A triple-differential measurement is performed as a function of the invariant mass and rapidity of the $$\hbox {t}{\bar{\hbox {t}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mtext>t</mml:mtext><mml:mover><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow><mml:mrow><mml:mo>¯</mml:mo></mml:mrow></mml:mover></mml:mrow></mml:math> system and the multiplicity of additional jets at particle level. The data are compared to predictions of Monte Carlo event generators that complement next-to-leading-order (NLO) quantum chromodynamics (QCD) calculations with parton showers. Together with a fixed-order NLO QCD calculation, the triple-differential measurement is used to extract values of the strong coupling strength $$\alpha _{S}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>α</mml:mi><mml:mi>S</mml:mi></mml:msub></mml:math> and the top quark pole mass ( $$m_{{\text {t}}}^{{\text {pole}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mi>m</mml:mi><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow><mml:mtext>pole</mml:mtext></mml:msubsup></mml:math> ) using several sets of parton distribution functions (PDFs). The measurement of $$m_{{\text {t}}}^{{\text {pole}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mi>m</mml:mi><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow><mml:mtext>pole</mml:mtext></mml:msubsup></mml:math> exploits the sensitivity of the $$\hbox {t}{\bar{\hbox {t}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mtext>t</mml:mtext><mml:mover><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow><mml:mrow><mml:mo>¯</mml:mo></mml:mrow></mml:mover></mml:mrow></mml:math> invariant mass distribution to $$m_{{\text {t}}}^{{\text {pole}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mi>m</mml:mi><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow><mml:mtext>pole</mml:mtext></mml:msubsup></mml:math> near the production threshold. Furthermore, a simultaneous fit of the PDFs, $$\alpha _{S}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>α</mml:mi><mml:mi>S</mml:mi></mml:msub></mml:math> , and $$m_{{\text {t}}}^{{\text {pole}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mi>m</mml:mi><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow><mml:mtext>pole</mml:mtext></mml:msubsup></mml:math> is performed at NLO, demonstrating that the new data have significant impact on the gluon PDF, and at the same time allow an accurate determination of $$\alpha _{S}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>α</mml:mi><mml:mi>S</mml:mi></mml:msub></mml:math> and $$m_{{\text {t}}}^{{\text {pole}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mi>m</mml:mi><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow><mml:mtext>pole</mml:mtext></mml:msubsup></mml:math> . The values $$\alpha _{S}(m_{{\text {Z}}}) = 0.1135{}^{+0.0021}_{-0.0017}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>α</mml:mi><mml:mi>S</mml:mi></mml:msub><mml:mrow><mml:mo>(</mml:mo><mml:msub><mml:mi>m</mml:mi><mml:mtext>Z</mml:mtext></mml:msub><mml:mo>)</mml:mo></mml:mrow><mml:mo>=</mml:mo><mml:mn>0.1135</mml:mn><mml:msubsup><mml:mrow/><mml:mrow><mml:mo>-</mml:mo><mml:mn>0.0017</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo><mml:mn>0.0021</mml:mn></mml:mrow></mml:msubsup></mml:mrow></mml:math> and $$m_{{\text {t}}}^{{\text {pole}}} = 170.5 \pm 0.8 \,{\text {GeV}} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msubsup><mml:mi>m</mml:mi><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow><mml:mtext>pole</mml:mtext></mml:msubsup><mml:mo>=</mml:mo><mml:mn>170.5</mml:mn><mml:mo>±</mml:mo><mml:mn>0.8</mml:mn><mml:mspace/><mml:mtext>GeV</mml:mtext></mml:mrow></mml:math> are extracted, which account for experimental and theoretical uncertainties, the latter being estimated from NLO scale variations. Possible effects from Coulomb and soft-gluon resummation near the $$\hbox {t}{\bar{\hbox {t}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mtext>t</mml:mtext><mml:mover><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow><mml:mrow><mml:mo>¯</mml:mo></mml:mrow></mml:mover></mml:mrow></mml:math> production threshold are neglected in these parameter extractions. A rough estimate of these effects indicates an expected correction of $$m_{{\text {t}}}^{{\text {pole}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mi>m</mml:mi><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow><mml:mtext>pole</mml:mtext></mml:msubsup></mml:math> of the order of $$+1 \,{\text {GeV}} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mo>+</mml:mo><mml:mn>1</mml:mn><mml:mspace/><mml:mtext>GeV</mml:mtext></mml:mrow></mml:math> , which can be regarded as additional theoretical uncertainty in the current $$m_{{\text {t}}}^{{\text {pole}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mi>m</mml:mi><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow><mml:mtext>pole</mml:mtext></mml:msubsup></mml:math> extraction.
Journal of High Energy Physics · 2020 · 56 citations
- Physics
- Particle physics
- Nuclear physics
A bstract A search for a heavy Higgs boson in the mass range from 0.2 to 3.0 TeV, decaying to a pair of W bosons, is presented. The analysis is based on proton-proton collisions at $$ \sqrt{s} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> </mml:math> = 13 TeV recorded by the CMS experiment at the LHC in 2016, corresponding to an integrated luminosity of 35.9 fb − 1 . The W boson pair decays are reconstructed in the 2ℓ2 ν and ℓ ν 2q final states (with ℓ = e or μ ). Both gluon fusion and vector boson fusion production of the signal are considered. Interference effects between the signal and background are also taken into account. The observed data are consistent with the standard model (SM) expectation. Combined upper limits at 95% confidence level on the product of the cross section and branching fraction exclude a heavy Higgs boson with SM-like couplings and decays up to 1870 GeV. Exclusion limits are also set in the context of a number of two-Higgs-doublet model formulations, further reducing the allowed parameter space for SM extensions.
Performance of the CMS Level-1 trigger in proton-proton collisions at √<i>s</i> = 13 TeV
Journal of Instrumentation · 2020 · 302 citations
- Computer Science
- Physics
- Particle physics
At the start of Run 2 in 2015, the LHC delivered proton-proton collisions at a center-of-mass energy of 13 TeV. During Run~2 (years 2015--2018) the LHC eventually reached a luminosity of 2.1 $\times$ 10$^{34}$ cm$^{-2}$ s$^{-1}$, almost three times that reached during Run 1 (2009-2013) and a factor of two larger than the LHC design value, leading to events with up to a mean of about 50 simultaneous inelastic proton-proton collisions per bunch crossing (pileup). The CMS Level-1 trigger was upgraded prior to 2016 to improve the selection of physics events in the challenging conditions posed by the second run of the LHC. This paper describes the performance of the CMS Level-1 trigger upgrade during the data taking period of 2016-2018. The upgraded trigger implements pattern recognition and boosted decision tree regression techniques for muon reconstruction, includes pileup subtraction for jets and energy sums, and incorporates pileup-dependent isolation requirements for electrons and tau leptons. In addition, the new trigger calculates high-level quantities such as the invariant mass of pairs of reconstructed particles. The upgrade reduces the trigger rate from background processes and improves the trigger efficiency for a wide variety of physics signals.
Extraction and validation of a new set of CMS pythia8 tunes from underlying-event measurements
The European Physical Journal C · 2020 · 407 citations
- Physics
- Particle physics
- Nuclear physics
New sets of CMS underlying-event parameters ("tunes") are presented for the pythia8 event generator. These tunes use the NNPDF3.1 parton distribution functions (PDFs) at leading (LO), next-to-leading (NLO), or next-to-next-to-leading (NNLO) orders in perturbative quantum chromodynamics, and the strong coupling evolution at LO or NLO. Measurements of charged-particle multiplicity and transverse momentum densities at various hadron collision energies are fit simultaneously to determine the parameters of the tunes. Comparisons of the predictions of the new tunes are provided for observables sensitive to the event shapes at LEP, global underlying event, soft multiparton interactions, and double-parton scattering contributions. In addition, comparisons are made for observables measured in various specific processes, such as multijet, Drell-Yan, and top quark-antiquark pair production including jet substructure observables. The simulation of the underlying event provided by the new tunes is interfaced to a higher-order matrix-element calculation. For the first time, predictions from pythia8 obtained with tunes based on NLO or NNLO PDFs are shown to reliably describe minimum-bias and underlying-event data with a similar level of agreement to predictions from tunes using LO PDF sets.
Journal of High Energy Physics · 2020 · 46 citations
- Physics
- Particle physics
- Nuclear physics
A bstract A search for physics beyond the standard model in events with at least three charged leptons (electrons or muons) is presented. The data sample corresponds to an integrated luminosity of 137 fb − 1 of proton-proton collisions at $$ \sqrt{s} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> </mml:math> = 13 TeV, collected with the CMS detector at the LHC in 2016–2018. The two targeted signal processes are pair production of type-III seesaw heavy fermions and production of a light scalar or pseudoscalar boson in association with a pair of top quarks. The heavy fermions may be manifested as an excess of events with large values of leptonic transverse momenta or missing transverse momentum. The light scalars or pseudoscalars may create a localized excess in the dilepton mass spectra. The results exclude heavy fermions of the type-III seesaw model for masses below 880 GeV at 95% confidence level in the scenario of equal branching fractions to each lepton flavor. This is the most restrictive limit on the flavor-democratic scenario of the type-III seesaw model to date. Assuming a Yukawa coupling of unit strength to top quarks, branching fractions of new scalar (pseudoscalar) bosons to dielectrons or dimuons above 0.004 (0.03) and 0.04 (0.03) are excluded at 95% confidence level for masses in the range 15–75 and 108–340 GeV, respectively. These are the first limits in these channels on an extension of the standard model with scalar or pseudoscalar particles.
Journal of High Energy Physics · 2020 · 81 citations
- Physics
- Particle physics
- Nuclear physics
A bstract A search is presented for additional scalar (H) or pseudoscalar (A) Higgs bosons decaying to a top quark pair in proton-proton collisions at a center-of-mass energy of 13 TeV. The data set analyzed corresponds to an integrated luminosity of 35.9 fb − 1 collected by the CMS experiment at the LHC. Final states with one or two charged leptons are considered. The invariant mass of the reconstructed top quark pair system and variables that are sensitive to the spin of the particles decaying into the top quark pair are used to search for signatures of the H or A bosons. The interference with the standard model top quark pair background is taken into account. A moderate signal-like deviation compatible with an A boson with a mass of 400 GeV is observed with a global significance of 1.9 standard deviations. New stringent constraints are reported on the strength of the coupling of the hypothetical bosons to the top quark, with the mass of the bosons ranging from 400 to 750 GeV and their total relative width from 0.5 to 25%. The results of the search are also interpreted in a minimal supersymmetric standard model scenario. Values of m A from 400 to 700 GeV are probed, and a region with values of tan β below 1.0 to 1.5, depending on m A , is excluded at 95% confidence level.
A measurement of the Higgs boson mass in the diphoton decay channel
Physics Letters B · 2020 · 165 citations
- Physics
- Particle physics
- Nuclear physics
A measurement of the mass of the Higgs boson in the diphoton decay channel is presented. This analysis is based on 35.9 fb -1 of proton-proton collision data collected during the 2016 LHC running period, with the CMS detector at a centre-of-mass energy of 13 TeV. A refined detector calibration and new analysis techniques have been used to improve the precision of this measurement. The Higgs boson mass is measured to be m H = 125.78 0.26 GeV. This is combined with a measurement of m H already performed in the H ZZ 4 decay channel using the same data set, giving m H = 125.46 0.16 GeV. This result, when further combined with an earlier measurement of m H using data collected in 2011 and 2012 with the CMS detector, gives a value for the Higgs boson mass of m H = 125.38 0.14 GeV. This is currently the most precise measurement of the mass of the Higgs boson.
Cast Lead-eutectic Solid And Liquid Scintillating Fiber Shower Calorimeters
1990 IEEE Nuclear Science Symposium Conference Record · 2005-08-24 · 3 citations
articleCompact cast lead-eutectic scintillating fiber and scintillating liquid capillary electromagnetic calorimeter modules have been constructed. Construction methods are described and results from lab bench tests and beam test results are presented, with energy resolutions about 1519%/dE. These calorimeters are prototypes for a muon g-2 experiment, and precision compensated calorimetry at the ssc.
Copper-scintillating fiber hadron calorimeter tower prototypes
IEEE Conference on Nuclear Science Symposium and Medical Imaging · 2003-01-02 · 2 citations
articleThe authors have constructed and tested seven projective scintillating fiber-copper absorber hadron calorimeter towers for high-energy hadron collider detectors. Each tower contained 2.25% by volume scintillating fibers, embedded between copper laminations, 10.6 lambda deep. A hadron energy resolution of sigma /E=91%/ square root E was obtained. Pions exhibited uniform response when scanned across boundaries between modules and through a range of incident angles with respect to the fibers. The e/ pi ratio is 1.08+or-0.02 for energies between 10 and 20 GeV, with a response of approximately 60 p.e./GeV. The muon Landau distributions well-resolved from pedestals were observed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Frequent coauthors
- 1841 shared
M. Lethuillier
Institute of Nuclear Physics of Lyon
- 1727 shared
V. Sordini
Institute of Nuclear Physics of Lyon
- 1725 shared
S. Perriès
Institute of Nuclear Physics of Lyon
- 1697 shared
E. Conte
Institut Pluridisciplinaire Hubert Curien
- 1682 shared
D. Blöch
Institut Pluridisciplinaire Hubert Curien
- 1676 shared
J. Andreä
Institut Pluridisciplinaire Hubert Curien
- 1660 shared
C. Collard
Institut Pluridisciplinaire Hubert Curien
- 1643 shared
M. Titov
Institut de Recherche sur les Lois Fondamentales de l'Univers
Awards & honors
- Panofsky Prize, American Physical Society (2017)
- Instrumentation Award, American Physical Society, Division o…
- Physics Breakthrough Prize in Fundamental Physics (2015)
- Most Distinguished Alumnus Award, Carnegie Mellon University…
- ASAHI Prize, 'Discovery of the Finite Mass of Neutrinos' (19…
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