0000000000160462
AUTHOR
M. Bender
Measurement of the Soft-Drop Jet Mass in pp Collisions at s=13 TeV with the ATLAS Detector
Jet substructure observables have significantly extended the search program for physics beyond the standard model at the Large Hadron Collider. The state-of-the-art tools have been motivated by the ...
Constraining the surface properties of effective Skyrme interactions
The purpose of this study is threefold: first, to identify a scheme for the determination of the surface energy coefficient a_surf that offers the best compromise between robustness, precision, and numerical efficiency; second, to analyze the correlation between values for a_surf and the characteristic energies of the fission barrier of Pu240; and third, to lay out a procedure how the deformation properties of the Skyrme energy density functional (EDF) can be constrained during the parameter fit. There are several frequently used possibilities to define and calculate the surface energy coefficient a_surf of effective interactions. The most direct access is provided by the model system of se…
Shape coexistence in the neutron-deficient even-even Hg182-188 isotopes studied via Coulomb excitation
Coulomb-excitation experiments to study electromagnetic properties of radioactive even-even Hg isotopes were performed with 2.85 MeV/nucleon mercury beams from REX-ISOLDE. Magnitudes and relative signs of the reduced E2 matrix elements that couple the ground state and low-lying excited states in Hg182-188 were extracted. Information on the deformation of the ground and the first excited 0+ states was deduced using the quadrupole sum rules approach. Results show that the ground state is slightly deformed and of oblate nature, while a larger deformation for the excited 0+ state was noted in Hg182,184. The results are compared to beyond mean field and interacting-boson based models and interp…
Measurement of exclusive γγ→ℓ+ℓ− production in proton–proton collisions at s=7 TeV with the ATLAS detector
This Letter reports a measurement of the exclusive gamma gamma -> l(+)l(-) (l = e, mu) cross-section in proton-proton collisions at a centre-of-mass energy of 7 TeV by the ATLAS experiment at the LHC, based on an integrated luminosity of 4.6 fb(-1). For the electron or muon pairs satisfying exclusive selection criteria, a fit to the dilepton acoplanarity distribution is used to extract the fiducial cross-sections. The cross-section in the electron channel is determined to be sigma(excl)(gamma gamma -> e+e-) = 0.428 +/- 0.035 (stat.) +/- 0.018 (syst.) pbfor a phase-space region with invariant mass of the electron pairs greater than 24GeV, in which both electrons have transverse momentum p(T)…
Probing the Quantum Interference between Singly and Doubly Resonant Top-Quark Production in pp Collisions at s=13 TeV with the ATLAS Detector
This Letter presents a normalized differential cross-section measurement in a fiducial phase-space region where interference effects between top-quark pair production and associated production of a single top quark with a W boson and a b-quark are significant. Events with exactly two leptons (ee, μμ, or eμ) and two b-tagged jets that satisfy a multiparticle invariant mass requirement are selected from 36.1 fb^{-1} of proton-proton collision data taken at sqrt[s]=13 TeV with the ATLAS detector at the LHC in 2015 and 2016. The results are compared with predictions from simulations using various strategies for the interference. The standard prescriptions for interference modeling are signifi…
Measurements of four-lepton production in pp collisions at s=8 TeV with the ATLAS detector
A search is presented for a high-mass Higgs boson in the , , , and decay modes using the ATLAS detector at the CERN Large Hadron Collider. The search uses proton-proton collision data at a centre-o ...
Deformation and mixing of coexisting shapes in neutron-deficient polonium isotopes
Coulomb-excitation experiments are performed with postaccelerated beams of neutron-deficient Po196,198,200,202 isotopes at the REX-ISOLDE facility. A set of matrix elements, coupling the low-lying states in these isotopes, is extracted. In the two heaviest isotopes, Po200,202, the transitional and diagonal matrix elements of the 2+1 state are determined. In Po196,198 multistep Coulomb excitation is observed, populating the 4+1,0+2, and 2+2 states. The experimental results are compared to the results from the measurement of mean-square charge radii in polonium isotopes, confirming the onset of deformation from Po196 onwards. Three model descriptions are used to compare to the data. Calculati…
The ATLAS Data Acquisition and High Level Trigger system
Journal of Instrumentation 11(06), P06008 (2016). doi:10.1088/1748-0221/11/06/P06008
First glimpse of the $N=82$ shell closure below $Z=50$ from masses of neutron-rich cadmium isotopes and isomers
We probe the $N=82$ nuclear shell closure by mass measurements of neutron-rich cadmium isotopes with the ISOLTRAP spectrometer at ISOLDE-CERN. The new mass of $^{132}$Cd offers the first value of the $N=82$, two-neutron shell gap below $Z=50$ and confirms the phenomenon of mutually enhanced magicity at $^{132}$Sn. Using the recently implemented phase-imaging ion-cyclotron-resonance method, the ordering of the low-lying isomers in $^{129}$Cd and their energies are determined. The new experimental findings are used to test large-scale shell-model, mean-field and beyond-mean-field calculations, as well as the ab initio valence-space in-medium similarity renormalization group.
First measurement of the rate K0L → πμνγ
Abstract In a preliminary version of the NA48 experiment at the CERN SPS, in which an iron-scintillator sandwich calorimeter was used as a photon detector, the ratio of K L → πμνγ and K L → πμν decays was measured. The branching ratio BR(K L →πμνγ, E γ ∗ ≥30 MeV )/(K L → πμν ) is found to be (2.08±0.17 +0.16 −0.21 )×10 −3 , where the first error is statistical and the second systematic. The result is in agreement with theoretical predictions.
In-beam gamma-ray and electron spectroscopy of $^{249,251}$Md
The odd-Z Md251 nucleus was studied using combined γ-ray and conversion-electron in-beam spectroscopy. Besides the previously observed rotational band based on the [521]1/2− configuration, another rotational structure has been identified using γ-γ coincidences. The use of electron spectroscopy allowed the rotational bands to be observed over a larger rotational frequency range. Using the transition intensities that depend on the gyromagnetic factor, a [514]7/2− single-particle configuration has been inferred for this band, i.e., the ground-state band. A physical background that dominates the electron spectrum with an intensity of ≃60% was well reproduced by simulating a set of unresolved ex…
Shape Coexistence in the Neutron-Deficient Even-EvenHg182−188Isotopes Studied via Coulomb Excitation
Coulomb-excitation experiments to study electromagnetic properties of radioactive even-even Hg isotopes were performed with 2.85 MeV/nucleon mercury beams from REX-ISOLDE. Magnitudes and relative signs of the reduced E2 matrix elements that couple the ground state and low-lying excited states in Hg182-188 were extracted. Information on the deformation of the ground and the first excited 0(+) states was deduced using the quadrupole sum rules approach. Results show that the ground state is slightly deformed and of oblate nature, while a larger deformation for the excited 0(+) state was noted in Hg-182; 184. The results are compared to beyond mean field and interacting-boson based models and i…
Constraints on off-shell Higgs boson production and the Higgs boson total width in ZZ → 4ℓ and ZZ → 2ℓ2ν final states with the ATLAS detector
A measurement of off-shell Higgs boson production in the and decay channels, where ℓ stands for either an electron or a muon, is performed using data from proton–proton collisions at a centre-of-mass energy of TeV. The data were collected by the ATLAS experiment in 2015 and 2016 at the Large Hadron Collider, and they correspond to an integrated luminosity of . An observed (expected) upper limit on the off-shell Higgs signal strength, defined as the event yield normalised to the Standard Model prediction, of 3.8 (3.4) is obtained at 95% confidence level (CL). Assuming the ratio of the Higgs boson couplings to the Standard Model predictions is independent of the momentum transfer of the Higgs…
Observation of the decay KS→π+π−e+e−
Abstract We present the first observation of the decay KS→π+π−e+e− based upon the data collected in 1998 by the NA48 experiment at CERN. We have identified a clean sample of 56 events with negligible background contamination. Using KL→π+π−π0D decays as normalization sample, the branching ratio is measured to be BR(KS→π+π−e+e−)=[4.5±0.7(stat)±0.4(syst)]×10−5. This result is in good agreement with the theoretical expectations from the mechanism of inner bremsstrahlung.
Measurement of jet charge in dijet events froms=8 TeVppcollisions with the ATLAS detector
The momentum-weighted sum of the charges of tracks associated to a jet is sensitive to the charge of the initiating quark or gluon. This paper presents a measurement of the distribution of momentum ...
Shape coexistence at the proton drip-line: First identification of excited states inPb180
Excited states in the extremely neutron-deficient nucleus {sup 180}Pb have been identified for the first time using the JUROGAM II array in conjunction with the RITU recoil separator at the Accelerator Laboratory of the University of Jyvaeskylae. This study lies at the limit of what is presently achievable with in-beam spectroscopy, with an estimated cross section of only 10 nb for the {sup 92}Mo({sup 90}Zr,2n){sup 180}Pb reaction. A continuation of the trend observed in {sup 182}Pb and {sup 184}Pb is seen, where the prolate minimum continues to rise beyond the N=104 midshell with respect to the spherical ground state. Beyond-mean-field calculations are in reasonable correspondence with the…
De-excitation of the strongly coupled band in 177Au and implications for core intruder configurations in the light Hg isotopes
International audience; Excited states in the proton-unbound nuclide $^{177}$Au were populated in the $^92}$Mo($^{88}$Sr, p2n) reaction and identified using the Jurogam-II and GREAT spectrometers in conjunction with the RITU gas-filled separator at the University of Jyväskylä Accelerator Laboratory. A strongly coupled band and its decay path to the 11/2−α-decaying isomer have been identified using recoil-decay tagging. Comparisons with cranked Hartree-Fock-Bogoliubov (HFB) calculations based on Skyrme energy functionals suggest that the band has a prolate deformation and is based upon coupling the odd 1h11/2 proton hole to the excited 02+ configuration in the $^{178}$Hg core. Although these…
Measurement of the differential cross-section of highly boosted top quarks as a function of their transverse momentum ins=8 TeVproton-proton collisions using the ATLAS detector
The differential cross-section for pair production of top quarks with high transverse momentum is measured in 20.3 fb(-1) of proton-proton collisions at a center-of-mass energy of 8 TeV. The measur ...
Search for Resonant and Nonresonant Higgs Boson Pair Production in the bb¯τ+τ− Decay Channel in pp Collisions at s=13 TeV with the ATLAS Detector
A search for resonant and nonresonant pair production of Higgs bosons in the b (b) over bar tau(+)tau(-) final state is presented. The search uses 36.1 fb(-1) of pp collision data with root s = 13 ...
γ-Ray Spectroscopy at the Limits: First Observation of Rotational Bands inLr255
The rotational band structure of Lr-255 has been investigated using advanced in-beam gamma-ray spectroscopic techniques. To date, Lr-255 is the heaviest nucleus to be studied in this manner. One ro ...
High-ET isolated-photon plus jets production in pp collisions at s=8 TeV with the ATLAS detector
The dynamics of isolated-photon plus one-, two- and three-jet production in pp collisions at a centre-of-mass energy of 8 TeV are studied with the ATLAS detector at the LHC using a data set with an ...
Shape coexistence at the proton drip-line: First identification of excited states in 180Pb
Excited states in the extremely neutron-deficient nucleus, 180Pb, have been identified for the first time using the JUROGAM II array in conjunction with the RITU recoil separator at the Accelerator Laboratory of the University of Jyvaskyla. This study lies at the limit of what is presently achievable with in-beam spectroscopy, with an estimated cross-section of only 10 nb for the 92Mo(90Zr,2n)180Pb reaction. A continuation of the trend observed in 182Pb and 184Pb is seen, where the prolate minimum continues to rise beyond the N=104 mid-shell with respect to the spherical ground state. Beyond mean-field calculations are in reasonable correspondence with the trends deduced from experiment.
Search for resonant WZ production in the fully leptonic final state in proton–proton collisions at s=13TeV with the ATLAS detector
A search for a heavy resonance decaying into WZ in the fully leptonic channel (electrons and muons) is performed. It is based on proton–proton collision data collected by the ATLAS experiment at the Large Hadron Collider at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 36.1 fb −1 . No significant excess is observed over the Standard Model predictions and limits are set on the production cross section times branching ratio of a heavy vector particle produced either in quark–antiquark fusion or through vector-boson fusion. Constraints are also obtained on the mass and couplings of a singly charged Higgs boson, in the Georgi–Machacek model, produced through ve…
Odd-odd neutron-rich rhodium isotopes studied with the double Penning trap JYFLTRAP
Precision mass measurements of neutron-rich rhodium isotopes have been performed at the JYFLTRAP Penning trap mass spectrometer at the Ion Guide Isotope Separator On-Line (IGISOL) facility. We report results on ground- and isomeric-state masses in $^{110,112,114,116,118}$Rh and the very first mass measurement of $^{120}$Rh. The isomeric states were separated and measured for the first time using the phase-imaging ion-cyclotron-resonance (PI-ICR) technique. For $^{112}$Rh, we also report new half-lives for both the ground state and the isomer. The results are compared to theoretical predictions using the BSkG1 mass model and discussed in terms of triaxial deformation.
Shell-model calculation of isospin-symmetry breaking correction to superallowed Fermi beta-decay
We investigate the radial-overlap part of the isospin-symmetry breaking correction to superallowed $0^+\to 0^+$-decay using the shell-model approach similar to that of Refs. [1, 2]. The 8 sd-shell emitters with masses between $A=22$ and $A=38$ have been re-examined. The Fermi matrix element is evaluated with realistic spherical single-particle wave functions, obtained from spherical Woods-Saxon (WS) or Hartree-Fock (HF) potentials, fine-tuned to reproduce the experimental data on charge radii and separation energies for nuclei of interest. The elaborated adjustment procedure removes any sensitivity of the correction to a specific parametrisation of the WS potential or to various versions of…
Measurement of photon?jet transverse momentum correlations in 5.02 TeV Pb + Pb and pp collisions with ATLAS
Jets created in association with a photon can be used as a calibrated probe to study energy loss in the medium created in nuclear collisions. Measurements of the transverse momentum balance between isolated photons and inclusive jets are presented using integrated luminosities of 0.49 nb−1 of Pb + Pb collision data at TeV and 25 pb−1 of pp collision data at TeV recorded with the ATLAS detector at the LHC. Photons with transverse momentum GeV and are paired with all jets in the event that have GeV and pseudorapidity . The transverse momentum balance given by the jet-to-photon ratio, , is measured for pairs with azimuthal opening angle . Distributions of the per-photon jet yield as a function…
Measurement of the quadratic slope parameter in the K-L -> 3 pi(0) decay Dalitz plot
A value of (-6.1 +- 0.9_{stat} +- 0.5_{syst})*10^{-3} is obtained for the quadratic slope parameter h in the K_L -> 3\pi^0 decay Dalitz plot at the NA48 experiment at the CERN SPS. The result is based on 14.7*10^6 fully reconstructed K_L -> 3\pi^0 -> 6\gamma decays. This is the most precise measurement of any of the Dalitz plot slope parameters in the charged and neutral kaon decays so far.
Measurement of D⁎±, D± and Ds± meson production cross sections in pp collisions at s=7 TeV with the ATLAS detector
The production of D*(+/-), D-+/- and D-S(+/-) charmed mesons has been measured with the ATLAS detector in pp collisions at,/7s = 7 TeV at the LHC, using data corresponding to an integrated luminosi ...
Observation of Higgs boson production in association with a top quark pair at the LHC with the ATLAS detector
Physics letters / B 784, 173 - 191 (2018). doi:10.1016/j.physletb.2018.07.035
Measurement of the decay rate and form factor parameter in the decay KL→e+e−γ
Abstract The decay rate of the neutral K meson KL→e+e−γ has been measured with the NA48 detector at the CERN SPS. A total of 6864 events has been observed with an estimated background of 10 events. The branching ratio is Γ(KL→e+e−γ)/Γ(KL→all) = (1.06±0.02stat±0.02sys±0.04calc)×10−5. The parameter α K ∗ describing the relative strength of the two contributing amplitudes to this decay through intermediate pseudoscalar or vector mesons was measured to be α K ∗ =−0.36±0.06stat±0.02sys.
In-beam γ-ray and electron spectroscopy of Md249,251
The odd-Z 251Md nucleus was studied using combined γ-ray and conversion-electron in-beam spectroscopy. Besides the previously observed rotational band based on the [521]1/2− configuration, another rotational structure has been identified using γ−γ coincidences. The use of electron spectroscopy allowed the rotational bands to be observed over a larger rotational frequency range. Using the transition intensities that depend on the gyromagnetic factor, a [514]7/2− single-particle configuration has been inferred for this band, i.e., the ground-state band. A physical background that dominates the electron spectrum with an intensity of ≃60% was well reproduced by simulating a set of unresolved ex…
Transverse momentum, rapidity, and centrality dependence of inclusive charged-particle production in sNN=5.02 TeV p+ Pb collisions measured by the ATLAS experiment
Measurements of the per-event charged-particle yield as a function of the charged-particle transverse momentum and rapidity are performed using p+Pbp+Pb collision data collected by the ATLAS experiment at the LHC at a centre-of-mass energy of sqrt (SNN) = 5.01 TeV. Charged particles are reconstructed over pseudorapidity |η|<2.3|η|<2.3 and transverse momentum between 0.1 GeV0.1 GeV and 22 GeV22 GeV in a dataset corresponding to an integrated luminosity of 1 μb−11 μb−1. The results are presented in the form of charged-particle nuclear modification factors, where the p+Pbp+Pb charged-particle multiplicities are compared between central and peripheral p+Pbp+Pb collisions as well as to charged-p…