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Author

Hamish Gordon

Other affiliations: CERN, Helsinki Institute of Physics, University of Leeds  ...read more
Bio: Hamish Gordon is an academic researcher from Carnegie Mellon University. The author has contributed to research in topics: Aerosol & Cloud condensation nuclei. The author has an hindex of 30, co-authored 69 publications receiving 4197 citations. Previous affiliations of Hamish Gordon include CERN & Helsinki Institute of Physics.


Papers
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Journal ArticleDOI
Jasmin Tröstl1, Wayne Chuang2, Hamish Gordon3, Martin Heinritzi4, Chao Yan5, Ugo Molteni1, Lars Ahlm6, Carla Frege1, F. Bianchi7, F. Bianchi5, F. Bianchi1, Robert Wagner5, Mario Simon4, Katrianne Lehtipalo1, Katrianne Lehtipalo5, Christina Williamson8, Christina Williamson4, Christina Williamson9, J. S. Craven10, Jonathan Duplissy11, Jonathan Duplissy5, Alexey Adamov5, Joao Almeida3, Anne-Kathrin Bernhammer12, Martin Breitenlechner12, Sophia Brilke4, Antonio Dias3, Sebastian Ehrhart3, Richard C. Flagan10, Alessandro Franchin5, Claudia Fuchs1, Roberto Guida3, Martin Gysel1, Armin Hansel12, Christopher R. Hoyle1, Tuija Jokinen5, Heikki Junninen5, Juha Kangasluoma5, Helmi Keskinen13, Helmi Keskinen5, Helmi Keskinen8, Jaeseok Kim13, Jaeseok Kim8, Manuel Krapf1, Andreas Kürten4, Ari Laaksonen13, Ari Laaksonen14, Michael J. Lawler13, Michael J. Lawler15, Markus Leiminger4, Serge Mathot3, Ottmar Möhler16, Tuomo Nieminen5, Tuomo Nieminen11, Antti Onnela3, Tuukka Petäjä5, Felix Piel4, Pasi Miettinen13, Matti P. Rissanen5, Linda Rondo4, Nina Sarnela5, Siegfried Schobesberger5, Siegfried Schobesberger8, Kamalika Sengupta17, Mikko Sipilä5, James N. Smith18, James N. Smith13, Gerhard Steiner19, Gerhard Steiner12, Gerhard Steiner5, António Tomé20, Annele Virtanen13, Andrea Christine Wagner4, Ernest Weingartner8, Ernest Weingartner1, Daniela Wimmer5, Daniela Wimmer4, Paul M. Winkler19, Penglin Ye2, Kenneth S. Carslaw17, Joachim Curtius4, Josef Dommen1, Jasper Kirkby3, Jasper Kirkby4, Markku Kulmala5, Ilona Riipinen6, Douglas R. Worsnop11, Douglas R. Worsnop5, Neil M. Donahue5, Neil M. Donahue2, Urs Baltensperger1 
26 May 2016-Nature
TL;DR: It is shown that organic vapours alone can drive nucleation, and a particle growth model is presented that quantitatively reproduces the measurements and implements a parameterization of the first steps of growth in a global aerosol model that can change substantially in response to concentrations of atmospheric cloud concentration nuclei.
Abstract: About half of present-day cloud condensation nuclei originate from atmospheric nucleation, frequently appearing as a burst of new particles near midday. Atmospheric observations show that the growth rate of new particles often accelerates when the diameter of the particles is between one and ten nanometres. In this critical size range, new particles are most likely to be lost by coagulation with pre-existing particles, thereby failing to form new cloud condensation nuclei that are typically 50 to 100 nanometres across. Sulfuric acid vapour is often involved in nucleation but is too scarce to explain most subsequent growth, leaving organic vapours as the most plausible alternative, at least in the planetary boundary layer. Although recent studies predict that low-volatility organic vapours contribute during initial growth, direct evidence has been lacking. The accelerating growth may result from increased photolytic production of condensable organic species in the afternoon, and the presence of a possible Kelvin (curvature) effect, which inhibits organic vapour condensation on the smallest particles (the nano-Kohler theory), has so far remained ambiguous. Here we present experiments performed in a large chamber under atmospheric conditions that investigate the role of organic vapours in the initial growth of nucleated organic particles in the absence of inorganic acids and bases such as sulfuric acid or ammonia and amines, respectively. Using data from the same set of experiments, it has been shown that organic vapours alone can drive nucleation. We focus on the growth of nucleated particles and find that the organic vapours that drive initial growth have extremely low volatilities (saturation concentration less than 10(-4.5) micrograms per cubic metre). As the particles increase in size and the Kelvin barrier falls, subsequent growth is primarily due to more abundant organic vapours of slightly higher volatility (saturation concentrations of 10(-4.5) to 10(-0.5) micrograms per cubic metre). We present a particle growth model that quantitatively reproduces our measurements. Furthermore, we implement a parameterization of the first steps of growth in a global aerosol model and find that concentrations of atmospheric cloud concentration nuclei can change substantially in response, that is, by up to 50 per cent in comparison with previously assumed growth rate parameterizations.

507 citations

Journal ArticleDOI
Jasper Kirkby1, Jasper Kirkby2, Jonathan Duplissy3, Jonathan Duplissy4, Kamalika Sengupta5, Carla Frege6, Hamish Gordon1, Christina Williamson2, Christina Williamson7, Martin Heinritzi8, Martin Heinritzi2, Mario Simon2, Chao Yan3, Joao Almeida2, Joao Almeida1, Jasmin Tröstl6, Tuomo Nieminen3, Tuomo Nieminen4, Ismael K. Ortega, Robert Wagner3, Alexey Adamov3, António Amorim9, Anne-Kathrin Bernhammer8, F. Bianchi6, F. Bianchi10, Martin Breitenlechner8, Sophia Brilke2, Xuemeng Chen3, J. S. Craven11, Antonio Dias1, Sebastian Ehrhart2, Sebastian Ehrhart1, Richard C. Flagan11, Alessandro Franchin3, Claudia Fuchs6, Roberto Guida1, Jani Hakala3, Christopher R. Hoyle6, Tuija Jokinen3, Heikki Junninen3, Juha Kangasluoma3, Jaeseok Kim7, Jaeseok Kim12, Manuel Krapf6, Andreas Kürten2, Ari Laaksonen12, Ari Laaksonen13, Katrianne Lehtipalo6, Katrianne Lehtipalo3, Vladimir Makhmutov14, Serge Mathot1, Ugo Molteni6, Antti Onnela1, Otso Peräkylä3, Felix Piel2, Tuukka Petäjä3, Arnaud P. Praplan3, Kirsty J. Pringle5, Alexandru Rap5, N. A. D. Richards5, Ilona Riipinen15, Matti P. Rissanen3, Linda Rondo2, Nina Sarnela3, Siegfried Schobesberger7, Siegfried Schobesberger3, Catherine E. Scott5, John H. Seinfeld11, Mikko Sipilä4, Mikko Sipilä3, Gerhard Steiner16, Gerhard Steiner3, Gerhard Steiner8, Yuri Stozhkov14, Frank Stratmann17, António Tomé18, Annele Virtanen12, Alexander L. Vogel1, Andrea Christine Wagner2, Paul E. Wagner16, Ernest Weingartner6, Daniela Wimmer2, Daniela Wimmer3, Paul M. Winkler16, Penglin Ye19, Xuan Zhang11, Armin Hansel8, Josef Dommen6, Neil M. Donahue19, Douglas R. Worsnop3, Douglas R. Worsnop12, Urs Baltensperger6, Markku Kulmala3, Markku Kulmala4, Kenneth S. Carslaw5, Joachim Curtius2 
26 May 2016-Nature
TL;DR: Ion-induced nucleation of pure organic particles constitutes a potentially widespread source of aerosol particles in terrestrial environments with low sulfuric acid pollution.
Abstract: Atmospheric aerosols and their effect on clouds are thought to be important for anthropogenic radiative forcing of the climate, yet remain poorly understood. Globally, around half of cloud condensation nuclei originate from nucleation of atmospheric vapours. It is thought that sulfuric acid is essential to initiate most particle formation in the atmosphere, and that ions have a relatively minor role. Some laboratory studies, however, have reported organic particle formation without the intentional addition of sulfuric acid, although contamination could not be excluded. Here we present evidence for the formation of aerosol particles from highly oxidized biogenic vapours in the absence of sulfuric acid in a large chamber under atmospheric conditions. The highly oxygenated molecules (HOMs) are produced by ozonolysis of α-pinene. We find that ions from Galactic cosmic rays increase the nucleation rate by one to two orders of magnitude compared with neutral nucleation. Our experimental findings are supported by quantum chemical calculations of the cluster binding energies of representative HOMs. Ion-induced nucleation of pure organic particles constitutes a potentially widespread source of aerosol particles in terrestrial environments with low sulfuric acid pollution.

502 citations

Journal ArticleDOI
Roel Aaij, A. A. Affolder1, Kazuyoshi Carvalho Akiba2, Michael Alexander3, S. Ali, Robert Appleby4, Marina Artuso5, A. Bates3, A. Bay6, O. Behrendt7, J. Benton8, M. van Beuzekom, P. M. Bjørnstad4, Galina Bogdanova9, Silvia Borghi4, A. Borgia5, T. J. V. Bowcock1, J. F. J. van den Brand, H. Brown1, Jan Buytaert7, O. Callot10, J. Carroll1, Gianluigi Casse1, P. Collins7, S. De Capua4, M. Doets, S. Donleavy1, D. Dossett11, R. Dumps7, Doris Eckstein, Lars Eklund3, C. Farinelli, S. Farry1, M. Ferro-Luzzi7, R. Frei6, J. Garofoli5, Marco Gersabeck4, T. J. Gershon11, A. Gong12, H. Gong12, Hamish Gordon7, Guido Haefeli6, J. Harrison4, V. Heijne, Karol Hennessy1, Wouter Hulsbergen, T. Huse13, David Hutchcroft1, A. Jaeger14, Pawel Jalocha15, E. Jans, Malcolm John15, James Keaveney16, Tjeerd Ketel, M. Korolev9, M. Kraan, T. Lastovicka17, George Lafferty4, T. E. Latham11, G. Lefeuvre5, Alexander Leflat9, M. Liles1, A. Van Lysebetten, G. MacGregor4, Franciole Da Cunha Marinho2, R. McNulty18, M. Merkin9, Dermot Moran19, R. Mountain5, I. Mous, J. Mylroie-Smith1, Matthew Needham20, Nikolay Nikitin9, A. Noor1, Agnieszka Oblakowska-Mucha21, A. Papadelis, M. Pappagallo3, C. Parkes4, G. D. Patel1, B. Rakotomiaramanana6, S. Redford7, M. M. Reid11, Kurt Rinnert1, Eduardo Rodrigues4, Aldo Saavedra22, Manuel Schiller, O. Schneider6, Tara Shears1, R. Silva Coutinho11, N. A. Smith1, Tomasz Szumlak21, C. Thomas15, J. van Tilburg, M. Tobin6, Jaap Velthuis8, B. Verlaat, Sébastien Viret23, V. Volkov9, C. Wallace11, Jing Wang5, A. D. Webber4, Mark Whitehead11, E. G. Zverev9 
TL;DR: The Vertex Locator (VELO) as discussed by the authors is a silicon microstrip detector that surrounds the proton-proton interaction region in the LHCb experiment, which is operated in vacuum and uses a bi-phase CO2 cooling system.
Abstract: The Vertex Locator (VELO) is a silicon microstrip detector that surrounds the proton-proton interaction region in the LHCb experiment The performance of the detector during the first years of its physics operation is reviewed The system is operated in vacuum, uses a bi-phase CO2 cooling system, and the sensors are moved to 7mm from the LHC beam for physics data taking The performance and stability of these characteristic features of the detector are described, and details of the material budget are given The calibration of the timing and the data processing algorithms that are implemented in FPGAs are described The system performance is fully characterised The sensors have a signal to noise ratio of approximately 20 and a best hit resolution of 4 mu m is achieved at the optimal track angle The typical detector occupancy for minimum bias events in standard operating conditions in 2011 is around 05%, and the detector has less than 1% of faulty strips The proximity of the detector to the beam means that the inner regions of the n(+)-on-n sensors have undergone space-charge sign inversion due to radiation damage The VELO performance parameters that drive the experiment's physics sensitivity are also given The track finding efficiency of the VELO is typically above 98% and the modules have been aligned to a precision of 1 mu m for translations in the plane transverse to the beam A primary vertex resolution of 13 mu m in the transverse plane and 71 mu m along the beam axis is achieved for vertices with 25 tracks An impact parameter resolution of less than 35 mu m is achieved for particles with transverse momentum greater than 1GeV/c

327 citations

Journal ArticleDOI
Roel Aaij, C. Abellan Beteta1, A. Adametz2, Bernardo Adeva3  +618 moreInstitutions (45)
TL;DR: In this article, the authors studied the LHCb's charmed hadron species in bins of transverse momentum and rapidity in the region 0

322 citations

Journal ArticleDOI
Georges Aad1, Brad Abbott2, Jalal Abdallah3, S. Abdel Khalek4  +2916 moreInstitutions (196)
TL;DR: In this paper, a measurement of the production processes of the recently discovered Higgs boson is performed in the two-photon final state using 4.5 fb(-1) of proton-proton collisions data at root s = 7 TeV and 20.4 GeV.
Abstract: A measurement of the production processes of the recently discovered Higgs boson is performed in the two-photon final state using 4.5 fb(-1) of proton-proton collisions data at root s = 7 TeV and 20.3 fb(-1) at root s = 8 TeV collected by the ATLAS detector at the Large Hadron Collider. The number of observed Higgs boson decays to diphotons divided by the corresponding Standard Model prediction, called the signal strength, is found to be mu = 1.17 +/- 0.27 at the value of the Higgs boson mass measured by ATLAS, m(H) = 125.4 GeV. The analysis is optimized to measure the signal strengths for individual Higgs boson production processes at this value of m(H). They are found to be mu(ggF) = 1.32 +/- 0.38, mu(VBF) = 0.8 +/- 0.7, mu(WH) = 1.0 +/- 1.6, mu(ZH) = 0.1(-0.1)(+3.7), and mu t (t) over barH = 1.6(-1.8)(+2.7), for Higgs boson production through gluon fusion, vector-boson fusion, and in association with a W or Z boson or a top-quark pair, respectively. Compared with the previously published ATLAS analysis, the results reported here also benefit from a new energy calibration procedure for photons and the subsequent reduction of the systematic uncertainty on the diphoton mass resolution. No significant deviations from the predictions of the Standard Model are found.

268 citations


Cited by
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TL;DR: In this paper, the ATLAS experiment is described as installed in i ts experimental cavern at point 1 at CERN and a brief overview of the expec ted performance of the detector is given.
Abstract: This paper describes the ATLAS experiment as installed in i ts experimental cavern at point 1 at CERN. It also presents a brief overview of the expec ted performance of the detector.

2,798 citations

Journal ArticleDOI
TL;DR: In this paper, the authors report world averages of measurements of b-hadron, c-, c-, and tau-lepton properties obtained by the Heavy Flavor Averaging Group (HFAG) using results available through the end of 2011.
Abstract: This article reports world averages of measurements of b-hadron, c-hadron, and tau-lepton properties obtained by the Heavy Flavor Averaging Group (HFAG) using results available through the end of 2011. In some cases results available in the early part of 2012 are included. For the averaging, common input parameters used in the various analyses are adjusted (rescaled) to common values, and known correlations are taken into account. The averages include branching fractions, lifetimes, neutral meson mixing parameters, CP violation parameters, parameters of semileptonic decays and CKM matrix elements.

2,151 citations

Journal ArticleDOI
Georges Aad1, Brad Abbott2, Jalal Abdallah3, Ovsat Abdinov4  +5117 moreInstitutions (314)
TL;DR: A measurement of the Higgs boson mass is presented based on the combined data samples of the ATLAS and CMS experiments at the CERN LHC in the H→γγ and H→ZZ→4ℓ decay channels.
Abstract: A measurement of the Higgs boson mass is presented based on the combined data samples of the ATLAS and CMS experiments at the CERN LHC in the H→γγ and H→ZZ→4l decay channels. The results are obtained from a simultaneous fit to the reconstructed invariant mass peaks in the two channels and for the two experiments. The measured masses from the individual channels and the two experiments are found to be consistent among themselves. The combined measured mass of the Higgs boson is mH=125.09±0.21 (stat)±0.11 (syst) GeV.

1,567 citations