Physics & Astronomy Publications

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Surface plasmon mediated harmonically resonant effects on third harmonic generation from Au and CuS nanoparticle films
(Nanophotonics, 2023-01-19) Spear, Nathan J.; Yan, Yueming; Queen, Joshua M.; Singh, Mahi R.; Macdonald, Janet E.; Haglund, Richard F.
A growing class of nonlinear materials employ the localized surface plasmonic resonance (LSPR) of nanoparticles to enhance harmonic generation. Material systems containing harmonically coupled metallic and semiconductor plasmonic nanoparticles have been shown to further increase performance. Here, we explore the effect of dual plasmonic interactions in bilayer CuS and Au nanoparticle films on third harmonic generation (THG). Detuning the CuS LSPR away from the excitation frequency changes the dominant upconversion pathway from THG to multiple photon photoluminescence (MPPL). Changing the size of the Au nanoparticle red shifts the LSPR from the second harmonic of the pump frequency and also eliminates the enhancement effect. When both LSPRs satisfy the harmonic condition, simultaneous excitation of CuS-Au nanoparticle films at the resonant frequency of each nanoparticle species enhances the generation of third harmonic light by sum-frequency generation, suggesting that the enhancement of THG in dually plasmonic nanoparticle films is the result of a cascaded nonlinear mechanism. An analytic model of the interaction between the plasmonic nanoparticles due to incoherent dipolar interactions is also presented. Understanding these processes opens a pathway for developing ultrafast, high-efficiency upconversion thin-film devices by clarifying the conditions that efficiently produce third harmonic generation without background MPPL or additional harmonics.
Independent Validation of the Temperate Super-Earth HD 79211 b using HARPS-N
(Astronomical Journal, 2023-02-01) Stassun, Keivan G.
We present high-precision radial velocities (RVs) from the HARPS-N spectrograph for HD79210 and HD79211, two M0V members of a gravitationally-bound binary system. We detect a planet candidate with a period of 24.421(-0.017)(+0.016) days around HD79211 in these HARPS-N RVs, validating the planet candidate originally identified in CARMENES RV data alone. Using HARPS-N, CARMENES and HIRES RVs spanning a total of 25 years, we further refine the planet candidate parameters to P = 24.422 +/- 0.014 days, K = 3.19 +/- 0.27 m s(-1), M sin i = 10.6 +/- 1.2M(circle plus), and a = 0.142 +/- 0.005 au. We do not find any additional planet candidate signals in the data of HD79211 nor do we find any planet candidate signals in HD79210. This system adds to the number of exoplanets detected in binaries with M dwarf members, and serves as a case study for planet formation in stellar binaries.
Backscattering and Line Broadening in Orion
(Astronomical Journal, 2022-12-19) O'Dell, C. R.; ; Mendez-Delgado, J. E.
Examination of emission lines in high-velocity-resolution optical spectra of the Orion Nebula confirms that the velocity component on the red wing of the main ionization front emission line is due to backscattering in the Photon Dominated Region. This scattered light component has a weak wavelength dependence that is consistent with either general interstellar medium particles or particles in the foreground of the Orion Nebula Cluster. An anomalous line-broadening component that has been known for 60+ years is characterized in unprecedented detail. Although this extra broadening may be due to turbulence along the line of sight of our spectra, we explore the possibility that it is due to Alfven waves in conditions where the ratio of magnetic and thermal energies are about equal and constant throughout the ionized gas.
A Low-mass Pre-main-sequence Eclipsing Binary in Lower Centaurus Crux Discovered with TESS
(The Astrophysical Journal, 2022-12-20) Stassun, Keivan G.; Torres, Guillermo; Kounkel, Marina; Feliz, Dax L.; Bouma, Luke G.; Howell, Steve B.; Gnilka, Crystal L.); Furlan, E.
We report the discovery of 2M1222-57 as a low-mass, pre-main-sequence (PMS) eclipsing binary (EB) in the Lower Centaurus Crux (LCC) association for which, using Gaia parallaxes and proper motions with a neural net age estimator, we determine an age of 16.2 +/- 2.2 Myr. The broadband spectral energy distribution (SED) shows clear excess at greater than or similar to 10 mu m indicative of a circumbinary disk, and new speckle imaging observations reveal a faint, tertiary companion separated by similar to 100 au. H alpha emission is modulated on the orbital period, consistent with theoretical models of orbitally pulsed accretion streams reaching from the inner disk edge to the central stars. From a joint analysis of spectroscopically determined radial velocities and TESS light curves, together with additional tight constraints provided by the SED and the Gaia parallax, we measure masses for the eclipsing stars of 0.74 M (circle dot) and 0.67 M (circle dot); radii of 0.98 R (circle dot) and 0.94 R (circle dot); and effective temperatures of 3750 K and 3645 K. The masses and radii of both stars are measured to an accuracy of similar to 1%. The measured radii are inflated, and the temperatures suppressed, relative to predictions of standard PMS evolutionary models at the age of LCC; also, the Li abundances are similar to 2 dex less depleted than predicted by those models. However, models that account for the global and internal effects of surface magnetic fields are able to simultaneously reproduce the measured radii, temperatures, and Li abundances at an age of 17.0 +/- 0.5 Myr. Altogether, the 2M1222-57 system presents very strong evidence that magnetic activity in young stars alters both their global properties and the physics of their interiors.
Dark Matter benchmark models for early LHC Run-2 Searches: Report of the ATLAS/CMS Dark Matter Forum
(Physics of the Dark Universe, 2020-01) Padeken, Klaas Ole
This document is the final report of the ATLAS-CMS Dark Matter Forum, a forum organized by the ATLAS and CMS collaborations with the participation of experts on theories of Dark Matter, to select a minimal basis set of dark matter simplified models that should support the design of the early LHC Run-2 searches. A prioritized, compact set of benchmark models is proposed, accompanied by studies of the parameter space of these models and a repository of generator implementations. This report also addresses how to apply the Effective Field Theory formalism for collider searches and present the results of such interpretations. (C) 2019 The Authors. Published by Elsevier B.V.
Migdal effect and photon bremsstrahlung in effective field theories of dark matter direct detection and coherent elastic neutrino-nucleus scattering
(Physical Review D, 2020-01-22) Bell, Nicole F.; Dent, James B.; Newstead, Jayden L.; Sabharwal, Subir; Weiler, Thomas J.
Dark matter direct detection experiments have limited sensitivity to light dark matter (below a few GeV), due to the challenges of lowering energy thresholds for the detection of nuclear recoil to below O(keV). While impressive progress has been made on this front, light dark matter remains the least constrained region of dark-matter parameter space. It has been shown that both ionization and excitation due to the Migdal effect arid coherently emitted photon bremsstrahlung from the recoiling atom can provide observable channels for light dark matter that would otherwise have been missed owing to the resulting nuclear recoil falling below the detector threshold. In this paper we extend previous work by calculating the Migdal effect and photon bremsstrahlung rates for a general set of interaction types, including those that are momentum independent or dependent, spin independent or dependent, as well as examining the rates for a variety of target materials, allowing us to place new experimental limits on some of these interaction types. Additionally, we include a calculation of these effects induced by the coherent scattering on nuclei of solar or atmospheric neutrinos. We demonstrate that the Migdal effect dominates over the bremsstrahlung effect for all targets considered for interactions induced by either dark matter or neutrinos. This reduces photon bremsstrahlung to irrelevancy for future direct detection experiments
Search for vectorlike leptons in multilepton final states in proton-proton collisions at root s=13 TeV
(Physical Review D, 2019-09-06) Greene, S.; Gurrola, A.; Janjam, R.; Johns, W.; Maguire, C.; Melo, A.; Ni, H.; Padeken, K.; Alvarez, . D. Ruiz; Sheldon, P.; Tuo, S.; Velkovska, J.; Verweij, M.; Xu, Q.
A search for vectorlike leptons in multilepton final states is presented. The data sample corresponds to an integrated luminosity of 77.4 fb(-1) of proton-proton collisions at a center-of-mass energy of 13 TeV collected by the CMS experiment at the LHC in 2016 and 2017. Events are categorized by the multiplicity of electrons, muons, and hadronically decaying tau leptons. The missing transverse momentum and the scalar sum of the lepton transverse momenta are used to distinguish the signal from background. The observed results are consistent with the expectations from the standard model hypothesis. The existence of a vectorlike lepton doublet, coupling to the third-generation standard model leptons in the mass range of 120-790 GeV, is excluded at 95% confidence level. These are the most stringent limits yet on the production of a vectorlike lepton doublet, coupling to the third-generation standard model leptons.
A search for pair production of new light bosons decaying into muons in proton-proton collisions at 13 TeV
(Physics Letters B, 2019-09-10) Greene, S.; Gurrola, A.; Janjam, R.; Johns, W.; Maguire, C.; Melo, A.; Ni, H.; Padeken, K.; Romeo, F.; Alvarez, J. D. Ruiz; Sheldon, P.; Tuo, S.; Velkovska, J.; Verweij, M.; Xu, Q.
A search for new light bosons decaying into muon pairs is presented using a data sample corresponding to an integrated luminosity of 35.9 fb(-1) of proton-proton collisions at a center-of-mass energy root s = 13 TeV, collected with the CMS detector at the CERN LHC. The search is model independent, only requiring the pair production of a new light boson and its subsequent decay to a pair of muons. No significant deviation from the predicted background is observed. A model independent limit is set on the product of the production cross section times branching fraction to dimuons squared times acceptance as a function of new light boson mass. This limit varies between 0.15 and 0.39 fb over a range of new light boson masses from 0.25 to 8.5 GeV. It is then interpreted in the context of the next-to-minimal supersymmetric standard model and a dark supersymmetry model that allows for nonnegligible light boson lifetimes. In both cases, there is significant improvement over previously published limits. (C) 2019 The Author(s). Published by Elsevier B.V.
Measurement of B-s(0) meson production in pp and PbPb collisions at root S-NN=5.02 TeV
(Physics Letter B, 2019-07-14) Greene, S.; Gurrola, A.; Janjam, R.; Johns, W.; Maguire, C.; Melo, A.; Ni, H.; Padeken, K.; Alvarez, J. D. Ruiz; Sheldon, P.; Tuo, S.; Velkovska, J.; Verweij, M.; Xu, Q.
The production cross sections of B-s(0) mesons and charge conjugates are measured in proton-proton (pp) and PbPb collisions via the exclusive decay channel B-s(0)-> J/ psi phi ->mu(+) mu(-) K+K- at a center-of-mass energy of 5.02 TeV per nucleon pair and within the rapidity range vertical bar y vertical bar < 2.4 using the CMS detector at the LHC. The pp measurement is performed as a function of transverse momentum (P-T) of the B-s(0), mesons in the range of 7 to 50 GeV/c and is compared to the predictions of perturbative QCD calculations. The B s production yield in PbPb collisions is measured in two F t intervals, 7 to 15 and 15 to 50 GeV/c, and compared to the yield in pp collisions in the same kinematic region. The nuclear modification factor (R-AA) is found to be 1.5 +/- 0.6(stat) +/- 0.5(syst) for 7-15 GeV/c, and 0.87 +/- 0.30(stat) +/- 0.1 7(syst) for 15-50 GeV/c, respectively. Within current uncertainties, the B-s(0) results are consistent with models of strangeness enhancement, and suppression by parton energy loss, as observed for the B+ mesons. Published by Elsevier B.V.
16TH INTERNATIONAL SYMPOSIUM ON CAPTURE GAMMA-RAY SPECTROSCOPY AND RELATED TOPICS (CGS16)
(16TH Internatinal Symposium on Capture Gamma-Ray Spectroscopy and Related Topics (CGS16), 2018) Luo, Y. X.; Hamilton, J. H.; Rasmussen, J. O.; Ramayya, A. V.; Frauendorf, S.; Wang, E.; Hwang, J. K.; Zhu, S.J.; Liu, Y. X.; Xu, F. R.; Sun, Y.; Liu, S. H.; Oganessian, Yu; Ma, W. C.
The paper reviews the systematic studies of triaxial deformations, new mode excitations and shape evolutions with regard to triaxial deformation in the neutron-rich nuclei with Z = 41-46, A similar to 100-116.
Space Telescope and Optical Reverberation Mapping Project. VIII. Time Variability of Emission and Absorption in NGC 5548 Based on Modeling the Ultraviolet Spectrum
(Astrophysical Journal, 2019-08-20) Somers, G.
We model the ultraviolet spectra of the Seyfert 1 galaxy NGC 5548 obtained with the Hubble Space Telescope during the 6 month reverberation mapping campaign in 2014. Our model of the emission from NGC 5548 corrects for overlying absorption and deblends the individual emission lines. Using the modeled spectra, we measure the response to continuum variations for the deblended and absorption-corrected individual broad emission lines, the velocity-dependent profiles of Ly alpha and C IV, and the narrow and broad intrinsic absorption features. We find that the time lags for the corrected emission lines are comparable to those for the original data. The velocity-binned lag profiles of Ly alpha and C IV have a double-peaked structure indicative of a truncated Keplerian disk. The narrow absorption lines show a delayed response to continuum variations corresponding to recombination in gas with a density of similar to 10(5) cm(-3). The high-ionization narrow absorption lines decorrelate from continuum variations during the same period as the broad emission lines. Analyzing the response of these absorption lines during this period shows that the ionizing flux is diminished in strength relative to the far-ultraviolet continuum. The broad absorption lines associated with the X-ray obscurer decrease in strength during this same time interval. The appearance of X-ray obscuration in similar to 2012 corresponds with an increase in the luminosity of NGC 5548 following an extended low state. We suggest that the obscurer is a disk wind triggered by the brightening of NGC 5548 following the decrease in size of the broad-line region during the preceding low-luminosity state.
Search for charged Higgs bosons in the H-+/- -> tau(+/-)nu(tau) decay channel in proton-proton collisions at s=13 TeV
(Journal of High Energy Physics, 2019-07-24) Greene, S.; Gurrola, A.; Janjam, R.; Johns, W.; Maguire, C.; Melo, A.; Ni, H.; Padeken, K.; Romeo, F.; Sheldon, P.; Tuo, S.; Velkovska, J.; Verweij, M.; Xu, Q.
A search is presented for charged Higgs bosons in the H-+/- -> tau(+/-)nu(tau) decay mode in the hadronic final state and in final states with an electron or a muon. The search is based on proton-proton collision data recorded by the CMS experiment in 2016 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb(-1). The results agree with the background expectation from the standard model. Upper limits at 95% confidence level are set on the production cross section times branching fraction to tau(+/-)nu(tau) for an H-+/- in the mass range of 80GeV to 3TeV, including the region near the top quark mass. The observed limit ranges from 6 pb at 80 GeV to 5 fb at 3 TeV. The limits are interpreted in the context of the minimal supersymmetric standard model m(h)(mod-) scenario.
Centrality and pseudorapidity dependence of the transverse energy density in pPb collisions ats root s(NN)=5.02 TeV
(Physical Review C, 2019-08-01) Greene, S.; Gurrola, A.; Janjam, R.; Johns, W.; Maguire, C.; Melo, A.; Ni, H.; Padeken, K.; Alvarez, J. D. Ruiz; Sheldon, P.; Tuo, S.; Velkovska, J.; Verweij, M.; Xu, Q.
The almost hermetic coverage of the CMS detector is used to measure the distribution of transverse energy, E-T, over 13.2 units of pseudorapidity, eta, for pPb collisions at a center-of-mass energy per nucleon pair of root s(NN) = 5.02 TeV. The huge angular acceptance exploits the fact that the CASTOR calorimeter at -6.6 < eta < -5.2 is effectively present on both sides of the colliding system because of a switch in the proton-going and lead-going beam directions. This wide acceptance enables the study of correlations between well-separated angular regions and makes the measurement a particularly powerful test of event generators. For minimum bias pPb collisions the maximum value of dE(T)/d eta is 22 GeV, which implies an E-T per participant nucleon pair comparable to that of peripheral PbPb collisions at root s(NN) 7 = 2.76 TeV. The increase of dE(T)/d eta with centrality is much stronger for the lead-going side than for the proton-going side. The i dependence of dE(T)/d eta is sensitive to the eta range in which the centrality variable is defined. Several modern generators are compared to these results but none is able to capture all aspects of the eta and centrality dependence of the data and the correlations observed between different eta regions.
An embedding technique to determine tau tau backgrounds in proton-proton collision data
(Journal of Instrumentation, 2019-06) Greene, S.; Gurrola, A.; Janjam, R.; Johns, W.; Maguire, C.; Melo, A.; Ni, H.; Padeken, K.; Romeo, F.; Sheldon, P.; Tuo, S.; Velkovska, J.; Verweij, M.; Xu, Q.
An embedding technique is presented to estimate standard model tau tau backgrounds from data with minimal simulation input. In the data, the muons are removed from reconstructed mu mu events and replaced with simulated tau leptons with the same kinematic properties. In this way, a set of hybrid events is obtained that does not rely on simulation except for the decay of the tau leptons. The challenges in describing the underlying event or the production of associated jets in the simulation are avoided. The technique described in this paper was developed for CMS. Its validation and the inherent uncertainties are also discussed. The demonstration of the performance of the technique is based on a sample of proton-proton collisions collected by CMS in 2017 at root s = 13 TeV corresponding to an integrated luminosity of 41.5 fb(-1).
Measurement of exclusive ρ(770)0 photoproduction in ultraperipheral pPb collisions at sNN−−−√=5.02TeV
(Experimental Physics, 2019-08-21) Greene, S.; Gurrola, A.; Janjam, R.; Johns, W.; Maguire, C.; Melo, A.; Ni, H.; Padeken, K.; Ruiz Alvarez, J. D.; Sheldon, P.; Tuo, S.; Velkovska, J.; Verweij, M.; Xu, Q.
Exclusive ρ(770)0 photoproduction is measured for the first time in ultraperipheral pPb collisions at sNN−−−√=5.02TeV with the CMS detector. The cross section σ(γp→ρ(770)0p) is 11.0±1.4(stat)±1.0(syst) μb at ⟨Wγp⟩=92.6GeV for photon–proton centre-of-mass energies Wγp between 29 and 213GeV. The differential cross section dσ/d|t| is measured in the interval 0.025<|t|<1GeV2 as a function of Wγp, where t is the squared four-momentum transfer at the proton vertex. The results are compared with previous measurements and theoretical predictions. The measured cross section σ(γp→ρ(770)0p) has a power-law dependence on the photon–proton centre-of-mass, consistent with electron–proton collision measurements performed at HERA. The Wγp dependence of the exponential slope of the differential cross section dσ/d|t| is also measured.
Anapole dark matter via vector boson fusion processes at the LHC
(Physical Review D, 2019-07-29) Florez, Andres; Gurrola, Alfredo; Johns, Will; Maruri, Jessica; Sheldon, Paul; Sinha, Kuver; Starko, Savanna Rae
Dark matter that is electrically neutral but couples to the electromagnetic current through higher-dimensional operators constitutes an interesting class of models. We investigate this class of models at the Large Hadron Collider, focusing on the anapole moment operator in an effective field theory (EFT) framework, and utilizing the vector boson fusion (VBF) topology. Assuming proton-proton collisions at root s = 13 TeV, we present the VBF anapole dark matter (ADM) cross sections and kinematic distributions as functions of the free parameters of the EFT, the cutoff scale Lambda and the ADM mass m(chi). We find that the distinctive VBF topology of two forward jets and large dijet pseudorapidity gap is effective at reducing SM backgrounds, leading to a 5 sigma discovery reach for all kinematically allowed ADM masses with Lambda <= 1.62 (1.1) TeV, assuming an integrated luminosity of 3000 (100) fb(-1).
An embedding technique to determine tau tau backgrounds in proton-proton collision data
(Journal of Instrumentation, 2019-06) Greene, S.; Gurrola, A.; Janjam, R.; Johns, W.; Maguire, C.; Melo, A.; Ni, H.; Padeken, K.; Romeo, F.; Sheldon, P.; Tuo, S.; Velkovska, J.; Verweij, M.; Xu, Q.
An embedding technique is presented to estimate standard model tau tau backgrounds from data with minimal simulation input. In the data, the muons are removed from reconstructed mu mu events and replaced with simulated tau leptons with the same kinematic properties. In this way, a set of hybrid events is obtained that does not rely on simulation except for the decay of the tau leptons. The challenges in describing the underlying event or the production of associated jets in the simulation are avoided. The technique described in this paper was developed for CMS. Its validation and the inherent uncertainties are also discussed. The demonstration of the performance of the technique is based on a sample of proton-proton collisions collected by CMS in 2017 at root s = 13 TeV corresponding to an integrated luminosity of 41.5 fb(-1).
Nuclear Dependence of the Transverse Single-Spin Asymmetry in the Production of Charged Hadrons at Forward Rapidity in Polarized p plus p, p plus Al, and p plus Au Collisions at root s(NN)=200 GeV
(Physical Review Letters, 2019-09-17) Greene, S.V.; Huang, S.; Morrow, S. I.; Peng, W.; Schaefer, B.; Tarafdar, S.; Velkovska, J.; Xu, Q.
We report on the nuclear dependence of transverse single-spin asymmetries (TSSAs) in the production of positively charged hadrons in polarized p(up arrow) + p, p(up arrow) + Al, and p(up arrow) + Au collisions at root s(NN) = 200 GeV. The measurements have been performed at forward rapidity (1.4 < eta < 2.4) over the range of transverse momentum (1.8 < p(T) < 7.0 GeV/c) and Feynman x (0.1 < x(F) < 0.2). We observed positive asymmetries for positively charged hadrons in p(up arrow) + p collisions, and significantly reduced asymmetries in p(up arrow) + A collisions. These results reveal a nuclear dependence of TSSAs for charged-hadron production in a regime where perturbative techniques are applicable. These results provide new opportunities to use p(up arrow) + A collisions as a tool to investigate the rich phenomena behind TSSAs in hadronic collisions and to use TSSAs as a new handle in studying small-system collisions.
H-band discovery of additional second-generation stars in the Galactic bulge globular cluster NGC 6522 as observed by APOGEE and Gaia
(ASTRONOMY & ASTROPHYSICS, 2019-07-22) Majewski, S.R.
We present an elemental abundance analysis of high-resolution spectra for five giant stars spatially located within the innermost regions of the bulge globular cluster NGC 6522 and derive Fe, Mg, Al, C, N, O, Si, and Ce abundances based on H-band spectra taken with the multi-object APOGEE-north spectrograph from the SDSS-IV Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey. Of the five cluster candidates, two previously unremarked stars are confirmed to have second-generation (SG) abundance patterns, with the basic pattern of depletion in C and Mg simultaneous with enrichment in N and Al as seen in other SG globular cluster populations at similar metallicity. In agreement with the most recent optical studies, the NGC 6522 stars analyzed exhibit (when available) only mild overabundances of the s-process element Ce, contradicting the idea that NGC 6522 stars are formed from gas enriched by spinstars and indicating that other stellar sources such as massive AGB stars could be the primary polluters of intra-cluster medium. The peculiar abundance signatures of SG stars have been observed in our data, confirming the presence of multiple generations of stars in NGC 6522.
Search for a W ' boson decaying to a tau lepton and a neutrino in proton-proton collisions at root s=13 TeV
(Physics Letters B, 2019-05-10) Greene, S.; Gurrola, A.; Janjam, R.; Johns, W.; Maguire, C.; Melo, A.; Ni, H.; Padeken, K.; Sheldon, P.; Tuo, S.; Velkovska, J.; Xu, Q.
A search for a new high-mass resonance decaying to a tau lepton and a neutrino is reported. The analysis uses proton-proton collision data collected by the CMS experiment at the LHC at root s= 13 TeV, corresponding to an integrated luminosity of 35.9 fb(-1). The search utilizes hadronically decaying tau leptons. No excess in the event yield is observed at high transverse masses of the tau and missing transverse momentum. An interpretation of results within the sequential standard model excludes W' boson masses below 4.0 TeV at 95% confidence level. Existing limits are also improved on models in which the W' boson decays preferentially to fermions of the third generation. Heavy W' bosons with masses less than 1.7-3.9 TeV, depending on the coupling in the non-universal G(221) model, are excluded at 95% confidence level. These are the most stringent limits on this model to date. (C) 2019 The Author(s). Published by Elsevier B.V.

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