Search for effective Lorentz and C P T violation using ZEUS data
Not Available
79 ASTRONOMY AND ASTROPHYSICS↗
Engineering topics
Gallo, E.
Publications and source records attributed to Gallo, E..
Impact of jet-production data on the next-to-next-to-leading-order determination of HERAPDF2.0 parton distributions
The HERAPDF2.0 ensemble of parton distribution functions (PDFs) was introduced in 2015. The final stage is presented, a next-to-next-to-leading-order (NNLO) analysis of the HERA data on inclusive deep inelastic ep scattering together with jet data as published by the H1 and ZEUS collaborations. A perturbative QCD fit, simultaneously of $\alpha _s(M_Z^2)$ and the PDFs, was performed with the result $\alpha _s(M_Z^2)= 0.1156 \pm 0.0011~\mathrm{(exp)}~ ^{+0.0001}_{-0.0002}~ \mathrm{(model}$ $\mathrm{+ parameterisation)}~ \pm 0.0029~\mathrm{(scale)}$. The PDF sets of HERAPDF2.0Jets NNLO were determined with separate fits using two fixed values of $\alpha _s(M_Z^2)$, $\alpha _s(M_Z^2)$ = 0.1155 and 0.118, since the latter value was already chosen for the published HERAPDF2.0 NNLO analysis based on HERA inclusive DIS data only. The different sets of PDFs are presented, evaluated and compared. The consistency of the PDFs determined with and without the jet data demonstrates the consistency of HERA inclusive and jet-production cross-section data. The inclusion of the jet data reduced the uncertainty on the gluon PDF. Predictions based on the PDFs of HERAPDF2.0Jets NNLO give an excellent description of the jet-production data used as input.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Probing effective field theory operators in the associated production of top quarks with a Z boson in multilepton final states at $\sqrt{s}$ = 13 TeV
A search for new top quark interactions is performed within the framework of an effective field theory using the associated production of either one or two top quarks with a Z boson in multilepton final states. The data sample corresponds to an integrated luminosity of 138 fb -1 of proton-proton collisions at √s = 13 TeV collected by the CMS experiment at the LHC. Five dimension-six operators modifying the electroweak interactions of the top quark are considered. Novel machine-learning techniques are used to enhance the sensitivity to effects arising from these operators. Distributions used for the signal extraction are parameterized in terms of Wilson coefficients describing the interaction strengths of the operators. All five Wilson coefficients are simultaneously fit to data and 95% confidence level intervals are computed. All results are consistent with the SM expectations.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
The CMS data analysis school experience
The CMS Data Analysis School is an official event organized by the CMS Collaboration to teach students and post-docs how to perform a physics analysis. The school is coordinated by the CMS schools committee and was first implemented at the LHC Physics Center at Fermilab in 2010. As part of the training, there are a number of “short” exercises on physics object reconstruction and identification, Monte Carlo simulation, and statistical analysis, which are followed by “long” exercises based on physics analyses. Some of the long exercises go beyond the current state of the art of the corresponding CMS analyses. This paper describes the goals of the school, the preparations for a school, the structure of the training, and student satisfaction with the experience as measured by surveys.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Test beam performance measurements for the Phase I upgrade of the CMS pixel detector
A new pixel detector for the CMS experiment was built in order to cope with the instantaneous luminosities anticipated for the Phase~I Upgrade of the LHC. The new CMS pixel detector provides four-hit tracking with a reduced material budget as well as new cooling and powering schemes. A new front-end readout chip mitigates buffering and bandwidth limitations, and allows operation at low comparator thresholds. Here in this paper, comprehensive test beam studies are presented, which have been conducted to verify the design and to quantify the performance of the new detector assemblies in terms of tracking efficiency and spatial resolution. Under optimal conditions, the tracking efficiency is $99.95\pm0.05\,\%$, while the intrinsic spatial resolutions are $4.80\pm0.25\,\mu \mathrm{m}$ and $7.99\pm0.21\,\mu \mathrm{m}$ along the $100\,\mu \mathrm{m}$ and $150\,\mu \mathrm{m}$ pixel pitch, respectively. The findings are compared to a detailed Monte Carlo simulation of the pixel detector and good agreement is found.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
The 2015 decay of the black hole X-ray binary V404 Cygni: robust disk-jet coupling and a sharp transition into quiescence
We present simultaneous X-ray and radio observations of the black hole X-ray binary V404 Cygni at the end of its 2015 outburst. From 2015 July 11–August 5, we monitored V404 Cygni with Chandra, Swift, and NuSTAR in the X-ray, and with the Karl G. Jansky Very Large Array and the Very Long Baseline Array in the radio, spanning a range of luminosities that were poorly covered during its previous outburst in 1989 (our 2015 campaign covers 2×10{sup 33}≲L{sub X}≲10{sup 34} erg s{sup −1}). During our 2015 campaign, the X-ray spectrum evolved rapidly from a hard photon index of Γ≈1.6 (at L{sub X}≈10{sup 34} erg s{sup −1}) to a softer Γ≈2 (at L{sub X}≈3×10{sup 33} erg s{sup −1}). We argue that V404 Cygni reaching Γ≈2 marks the beginning of the quiescent spectral state, which occurs at a factor of ≈3–4 higher X-ray luminosity than the average pre-outburst luminosity of ≈8×10{sup 32} erg s{sup −1}. V404 Cygni falls along the same radio/X-ray luminosity correlation that it followed during its previous outburst in 1989, implying a robust disk-jet coupling. We exclude the possibility that a synchrotron-cooled jet dominates the X-ray emission in quiescence, leaving synchrotron self-Compton from either a hot accretion flow or from a radiatively cooled jet as the most likely sources of X-ray radiation, and/or particle acceleration along the jet becoming less efficient in quiescence. Finally, we present the first indications of correlated radio and X-ray variability on minute timescales in quiescence, tentatively measuring the radio emission to lag the X-ray by 15±4 minute, suggestive of X-ray variations propagating down a jet with a length of <3.0 au.
79 ASTRONOMY AND ASTROPHYSICS↗
X-ray detected active galactic nuclei in dwarf galaxies at 0 < z < 1
We present a sample of accreting supermassive black holes (SMBHs) in dwarf galaxies at z<1. We identify dwarf galaxies in the NEWFIRM Medium Band Survey with stellar masses of M{sub ⋆}<3×10{sup 9} M{sub ⊙} that have spectroscopic redshifts from the DEEP2 survey and lie within the region covered by deep (flux limit of ∼5×10{sup −17}--6×10{sup −16} erg cm{sup −2} s{sup −1}) archival Chandra X-ray data. From our sample of 605 dwarf galaxies, 10 exhibit X-ray emission consistent with that arising from active galactic nucleus (AGN) activity. If black-hole mass scales roughly with stellar mass, then we expect that these AGNs are powered by SMBHs with masses of ∼10{sup 5}--10{sup 6} M{sub ⊙} and typical Eddington ratios of ∼5%. Furthermore, we find an AGN fraction consistent with extrapolations of other searches of ∼0.6%--3% for 10{sup 9} M{sub ⊙}⩽M{sub ⋆}⩽3×10{sup 9} M{sub ⊙} and 0.1<z<0.6. Our AGN fraction is in good agreement with a semi-analytic model, suggesting that, as we search larger volumes, we may use comparisons between observed AGN fractions and models to understand seeding mechanisms in the early universe.
79 ASTRONOMY AND ASTROPHYSICS↗
The Accretion Disk Wind in the Black Hole GRS 1915 + 105
We report on a 120 kiloseconds Chandra/HETG spectrum of the black hole GRS 1915+105. The observation was made during an extended and bright soft state in 2015 June. An extremely rich disk wind absorption spectrum is detected, similar to that observed at lower sensitivity in 2007. The very high resolution of the third-order spectrum reveals four components to the disk wind in the Fe K band alone; the fastest has a blueshift of v = 0.03 c (velocity equals 0.03 the speed of light). Broadened reemission from the wind is also detected in the first-order spectrum, giving rise to clear accretion disk P Cygni profiles. Dynamical modeling of the re-emission spectrum gives wind launching radii of r approximately equal to 10 (sup 2-4) GM (Gravitational constant times Mass) divided by c (sup 2) (the speed of light squared). Wind density values of n approximately equal to 10 (sup 13-16) per cubic centimeter are then required by the ionization parameter formalism. The small launching radii, high density values, and inferred high mass outflow rates signal a role for magnetic driving. With simple, reasonable assumptions, the wind properties constrain the magnitude of the emergent magnetic field to be B approximately equal to 10 (sup 3-4) G (Gravitational constant) if the wind is driven via magnetohydrodynamic (MHD) pressure from within the disk and B approximately equal to 10 (sup 4-5) G (Gravitational constant) if the wind is driven by magnetocentrifugal acceleration. The MHD estimates are below upper limits predicted by the canonical alpha-disk model. We discuss these results in terms of fundamental disk physics and black hole accretion modes.
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An Evolving Compact Jet in the Black Hole X-Ray Binary Maxi J1836-194
We report striking changes in the broadband spectrum of the compact jet of the black hole transient MAXI J1836−194 over state transitions during its discovery outburst in 2011. A fading of the optical-infrared (IR) flux occurred as the source entered the hard-intermediate state, followed by a brightening as it returned to the hard state. The optical-IR spectrum was consistent with a power law from optically thin synchrotron emission, except when the X-ray spectrum was softest. By fitting the radio to optical spectra with a broken power law, we constrain the frequency and flux of the optically thick/thin break in the jet synchrotron spectrum. The break gradually shifted to higher frequencies as the source hardened at X-ray energies, from approx 10(exp 11) to approx 4 × 10(exp 13) Hz. The radiative jet luminosity integrated over the spectrum appeared to be greatest when the source entered the hard state during the outburst decay (although this is dependent on the high-energy cooling break, which is not seen directly), even though the radio flux was fading at the time. The physical process responsible for suppressing and reactivating the jet (neither of which are instantaneous but occur on timescales of weeks) is uncertain, but could arise from the varying inner accretion disk radius regulating the fraction of accreting matter that is channeled into the jet. This provides an unprecedented insight into the connection between inflow and outflow, and has implications for the conditions required for jets to be produced, and hence their launching process.
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