PH
P. H. Hansen
Particle physics theoretical and experimental studies
University of Copenhagen
About
Research focus
Particle physics theoretical and experimental studies
Impact
5,133 pubs · 312,078 cites · h-index 217
Affiliations
Publications
Original Research
AUG 2024AadJournal of Instrumentation
Accuracy versus precision in boosted top tagging with the ATLAS detector
The identification of top quark decays where the top quark has a large momentum transverse to the beam axis, known as top tagging , is a crucial component in many measurements of Standard Model processes and searches for beyond the Standard Model physics at the Large Hadron Collider. Machine learning techniques have improved the performance of top tagging algorithms, but the size of the systematic uncertainties for all proposed algorithms has not been systematically studied. This paper presents the performance of several machine learning based top tagging algorithms on a dataset constructed from simulated proton-proton collision events measured with the ATLAS detector at √ s = 13 TeV. The systematic uncertainties associated with these algorithms are estimated through an approximate procedure that is not meant to be used in a physics analysis, but is appropriate for the level of precision required for this study. The most performant algorithms are found to have the largest uncertainties, motivating the development of methods to reduce these uncertainties without compromising performance. To enable such efforts in the wider scientific community, the datasets used in this paper are made publicly available.
Original Research
DEC 2018Monk
A Wavelet Based Pile-Up Mitigation Method for the LHC Upgrade
Collision experiments at the Large Hadron Collider suffer from the problem of pile-up, which is the read-out of multiple simultaneous background proton-proton collisions per beam-crossing. We introduce a pile-up mitigation technique based on wavelet decomposition. Pile-up is treated as a form of white noise, which can be removed by filtering beam-crossing events in the wavelet domain. The particle-level performance of the method is evaluated using a sample of simulated proton-proton collision events that contain Z bosons decaying to a pair of neutrinos, overlaid with pile-up. In the wavelet representation, the pile-up noise level is found to grow with the square root of the number of background proton-proton collisions.
Original Research
AUG 2004SchaelPhysics Letters B
Search for pentaquark states in Z decays
Exotic hadrons made of five quarks (pentaquarks) are searched for in hadronic Z decays collected by the ALEPH detector at LEP. No significant signal is observed. At 95% C.L., upper limits are set on the production rates N of such particles and their charge-conjugate state per Z decay.
Original Research
MAY 2003HeisterPhysics Letters B
A measurement of the gluon splitting rate into cc pairs in hadronic Z decays
The rate of gluon splitting into c c ̄ pairs in hadronic Z decays is measured using the data sample collected by ALEPH from 1991 to 1995. The selection is based on the identification of leptons (electrons and muons) originating from semileptonic charm decays, and on the topological properties of signal events. The result derived from the selected sample is g c c ̄ =(3.26±0.23( stat )±0.42( syst )) %.
Original Research
JAN 1982SakaiApplied Optics
Infrared emission spectroscopy of glow discharge formed in low pressure atmospheric gases
Laboratory study was conducted on the molecular and atomic emissions which are considered detectable in the IR radiative background of the upper atmosphere. The IR spectra of glow discharge emission formed in air and other atmospheric constituent gases of 0.1-Torr pressure and a 30-m long column were surveyed using the technique of Fourier spectroscopy. Several features hitherto unobserved were detected in our survey study.
Original Research
OCT 1979CrabbPhysical Review Letters
Spin-Spin Forces in 6-GeV/cNeutron-Proton Elastic Scattering
Measurement was made of dσdt for n_↑+p_↑→n+p at P_⊥²=0.8 and 1.0 (GeV/c)² at 6 GeV/c. The 6-GeV/c 53%-polarized neutrons from the 12-GeV/c polarized deuteron beam at the Argonne zero-gradient synchroton were scattered from our 75%-polarized proton target. Both spins were oriented perpendicular to the scattering plane. We found large unexpected spin-spin effects in n-p elastic scattering which are quite different from the p-p spin-spin effects.
Original Research
JUN 1977HansenPhysical review. D. Particles, fields, gravitation, and cosmology/Physical review. D. Particles and fields
Universal fit to p−p elastic diffraction scattering from the Lorentz-contracted geometrical model
We examine the prediction of the Lorentz-contracted geometrical model for proton-proton elastic scattering at small angles. The model assumes that when two high-energy particles collide, each behaves as a geometrical object which has a Gaussian density and is spherically symmetric except for the Lorentz contraction in the incident direction. It predicted that dσdt should be independent of energy when plotted against the variable β²P_⊥²σₜₒₜ(s)(38.3 mb). Thus the energy dependence of the diffraction-peak slope (b in an e^-b|t| plot) is given by b(s)=A²β²σₜₒₜ(s)(38.3 mb), where β is the proton's c.m. velocity and A is its radius. We used recently measured values of σₜₒₜ(s), and obtained an excellent fit to the elastic slope in both t regions [-t<0.1 (GeV/c)² and 0.1<-t<0.4 (GeV/c)²] at all energies from s=6 to 4000 (GeV)².
Original Research
FEB 1973HansenApplied Optics
Seventh Series of Atomic Hydrogen
Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text Peter Hansen and John Strong, "Seventh Series of Atomic Hydrogen," Appl. Opt. 12, 429-430 (1973) Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article
Original Research
MAR 1972HansenApplied Optics
High Resolution Hadamard Transform Spectrometer
The ir spectrometer described employs alkaline halide lenses, an echelle grating, and a cryogenically cooled doped germanium bolometer as a detector. It is provided for two possible modes of operation: one is a single slit or conventional scan, the other is a multiplex or Hadamard scan. Signal strength, noise characteristics, scanning time, and available computer facilities determine the mode of operation. Sample spectra are presented.