3,088 research outputs found
High-precision measurements from LHC to FCC-ee
This document provides a writeup of all contributions to the workshop on
"High precision measurements of : From LHC to FCC-ee" held at CERN,
Oct. 12--13, 2015. The workshop explored in depth the latest developments on
the determination of the QCD coupling from 15 methods where high
precision measurements are (or will be) available. Those include low-energy
observables: (i) lattice QCD, (ii) pion decay factor, (iii) quarkonia and (iv)
decays, (v) soft parton-to-hadron fragmentation functions, as well as
high-energy observables: (vi) global fits of parton distribution functions,
(vii) hard parton-to-hadron fragmentation functions, (viii) jets in p
DIS and -p photoproduction, (ix) photon structure function in
-, (x) event shapes and (xi) jet cross sections in
collisions, (xii) W boson and (xiii) Z boson decays, and (xiv) jets and (xv)
top-quark cross sections in proton-(anti)proton collisions. The current status
of the theoretical and experimental uncertainties associated to each extraction
method, the improvements expected from LHC data in the coming years, and future
perspectives achievable in collisions at the Future Circular Collider
(FCC-ee) with (1--100 ab) integrated luminosities yielding
10 Z bosons and jets, and 10 W bosons and leptons, are
thoroughly reviewed. The current uncertainty of the (preliminary) 2015 strong
coupling world-average value, = 0.1177 0.0013, is about
1\%. Some participants believed this may be reduced by a factor of three in the
near future by including novel high-precision observables, although this
opinion was not universally shared. At the FCC-ee facility, a factor of ten
reduction in the uncertainty should be possible, mostly thanks to
the huge Z and W data samples available.Comment: 135 pages, 56 figures. CERN-PH-TH-2015-299, CoEPP-MN-15-13. This
document is dedicated to the memory of Guido Altarell
Impact of dopants on the electrical properties in ABO3 perovskite type materials
The ceramics materials with ABO3 structure based on iron or silver doped sodium tantalate, were successfully synthesized using the ultrasonically method with immersed sonotrode in the reaction medium followed by heat treatment at 600°C. Samples were doped with silver for the A site of the perovskite lattice and with iron for the B site. The doping was performed in order to improve the electrical properties through change the crystalline structure and prevent ordering of the oxygen vacancies in these materials. The obtained materials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), BET analysis, energy-dispersive Xray spectroscopy (EDX) and electrical measurements. Structural analysis shows that the obtained materials have cubic structure and a homogeneous composition, without secondary compounds. Electrical measurements indicate that the presence of metal ions of iron or silver in the structure of NaTaO3 lead to decreases of the gap band energy, resulting in increase of electric conductivity
Effect of PD addition in lanthanum manganite : morpho-structural and electrical properties
LaMnO3 is an inorganic compound with perovskite structure and partial substitution of lanthanum ions [1] or manganese ions [2] has an effect on the physical properties of materials. In the present work we report the synthesis of LaMn1−x PdxO3 (with x = 0.2 and 0.3) materials at low temperature. The doping was performed in order to improve the electrical properties by changing the crystalline structure and prevent ordering of the oxygen vacancies in these materials. The obtained materials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), BET analysis, energy-dispersive X-ray spectroscopy (EDX) and electrical measurements. Structural analysis shows that the obtained materials crystallize in cubic structure and have a homogeneous composition, without secondary compounds
Dpes massless QCD have vacuum energy?
It is widely thought that this question has a positive answer, but we argue
that the support for this belief from both experiment and theory is weak or
nonexistent. We then list some of the ramifications of a negative answer.Comment: 8 pages, no figures, version to appear in NJ
Study of Upsilon(3S,2S) -> eta Upsilon(1S) and Upsilon(3S,2S) -> pi+pi- Upsilon(1S) hadronic trasitions
We study the Upsilon(3S,2S)->eta Upsilon(1S) and Upsilon(3S,2S)->pi+pi-
Upsilon(1S) transitions with 122 million Upsilon(3S) and 100 million
Upsilon(2S) mesons collected by the BaBar detector at the PEP-II asymmetric
energy e+e- collider. We measure B[Upsilon(2S)->eta
Upsilon(1S)]=(2.39+/-0.31(stat.)+/-0.14(syst.))10^-4 and Gamma[Upsilon(2S)->eta
Upsilon(1S)]/Gamma[Upsilon(2S)-> pi+pi-
Upsilon(1S)]=(1.35+/-0.17(stat.)+/-0.08(syst.))10^-3. We find no evidence for
Upsilon(3S)->eta Upsilon(1S) and obtain B[Upsilon(3S)->eta Upsilon(1S)]<1.0
10^-4 and Gamma[Upsilon(3S)->eta Upsilon(1S)]/Gamma[Upsilon(3S)->pi+pi-
Upsilon(1S)]<2.3 10^-3 as upper limits at the 90% confidence level. We also
provide improved measurements of the Upsilon(2S) - Upsilon(1S) and Upsilon(3S)
- Upsilon(1S) mass differences, 562.170+/-0.007(stat.)+/-0.088(syst.) MeV/c^2
and 893.813+/-0.015(stat.)+/-0.107(syst.) MeV/c^2 respectively.Comment: 8 pages, 16 encapsulated postscript figures, submitted to Phys.Rev.
Cross Sections for the Reactions e+e- --> K+ K- pi+pi-, K+ K- pi0pi0, and K+ K- K+ K- Measured Using Initial-State Radiation Events
We study the processes e+e- --> K+ K- pi+pi-gamma, K+ K- pi0pi0gamma, and K+
K- K+ K-gamma, where the photon is radiated from the initial state. About
84000, 8000, and 4200 fully reconstructed events, respectively, are selected
from 454 fb-1 of BaBar data. The invariant mass of the hadronic final state
defines the \epem center-of-mass energy, so that the K+ K- pi+pi- data can be
compared with direct measurements of the e+e- --> K+ K- pi+pi- reaction. No
direct measurements exist for the e+e- --> K+ K-pi0pi0 or e+e- --> K+ K-K+ K-
reactions, and we present an update of our previous result with doubled
statistics. Studying the structure of these events, we find contributions from
a number of intermediate states, and extract their cross sections. In
particular, we perform a more detailed study of the e+e- --> phi(1020)pipigamma
reaction, and confirm the presence of the Y(2175) resonance in the phi(1020)
f0(980) and K+K-f0(980) modes. In the charmonium region, we observe the J/psi
in all three final states and in several intermediate states, as well as the
psi(2S) in some modes, and measure the corresponding product of branching
fraction and electron width.Comment: 35 pages, 42 figure
Evidence for the h_b(1P) meson in the decay Upsilon(3S) --> pi0 h_b(1P)
Using a sample of 122 million Upsilon(3S) events recorded with the BaBar
detector at the PEP-II asymmetric-energy e+e- collider at SLAC, we search for
the spin-singlet partner of the P-wave chi_{bJ}(1P) states in the
sequential decay Upsilon(3S) --> pi0 h_b(1P), h_b(1P) --> gamma eta_b(1S). We
observe an excess of events above background in the distribution of the recoil
mass against the pi0 at mass 9902 +/- 4(stat.) +/- 2(syst.) MeV/c^2. The width
of the observed signal is consistent with experimental resolution, and its
significance is 3.1sigma, including systematic uncertainties. We obtain the
value (4.3 +/- 1.1(stat.) +/- 0.9(syst.)) x 10^{-4} for the product branching
fraction BF(Upsilon(3S)-->pi0 h_b) x BF(h_b-->gamma eta_b).Comment: 8 pages, 4 postscript figures, submitted to Phys. Rev. D (Rapid
Communications
First Observation of CP Violation in B0->D(*)CP h0 Decays by a Combined Time-Dependent Analysis of BaBar and Belle Data
We report a measurement of the time-dependent CP asymmetry of B0->D(*)CP h0
decays, where the light neutral hadron h0 is a pi0, eta or omega meson, and the
neutral D meson is reconstructed in the CP eigenstates K+ K-, K0S pi0 or K0S
omega. The measurement is performed combining the final data samples collected
at the Y(4S) resonance by the BaBar and Belle experiments at the
asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The
data samples contain ( 471 +/- 3 ) x 10^6 BB pairs recorded by the BaBar
detector and ( 772 +/- 11 ) x 10^6, BB pairs recorded by the Belle detector. We
measure the CP asymmetry parameters -eta_f S = +0.66 +/- 0.10 (stat.) +/- 0.06
(syst.) and C = -0.02 +/- 0.07 (stat.) +/- 0.03 (syst.). These results
correspond to the first observation of CP violation in B0->D(*)CP h0 decays.
The hypothesis of no mixing-induced CP violation is excluded in these decays at
the level of 5.4 standard deviations.Comment: 9 pages, 2 figures, submitted to Physical Review Letter
Single hadron response measurement and calorimeter jet energy scale uncertainty with the ATLAS detector at the LHC
The uncertainty on the calorimeter energy response to jets of particles is
derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the
calorimeter response to single isolated charged hadrons is measured and
compared to the Monte Carlo simulation using proton-proton collisions at
centre-of-mass energies of sqrt(s) = 900 GeV and 7 TeV collected during 2009
and 2010. Then, using the decay of K_s and Lambda particles, the calorimeter
response to specific types of particles (positively and negatively charged
pions, protons, and anti-protons) is measured and compared to the Monte Carlo
predictions. Finally, the jet energy scale uncertainty is determined by
propagating the response uncertainty for single charged and neutral particles
to jets. The response uncertainty is 2-5% for central isolated hadrons and 1-3%
for the final calorimeter jet energy scale.Comment: 24 pages plus author list (36 pages total), 23 figures, 1 table,
submitted to European Physical Journal
Measurement of the flavour composition of dijet events in pp collisions at root s=7 TeV with the ATLAS detector
This paper describes a measurement of the flavour composition of dijet events produced in pp collisions at √s=7 TeV using the ATLAS detector. The measurement uses the full 2010 data sample, corresponding to an integrated luminosity of 39 pb−1. Six possible combinations of light, charm and bottom jets are identified in the dijet events, where the jet flavour is defined by the presence of bottom, charm or solely light flavour hadrons in the jet. Kinematic variables, based on the properties of displaced decay vertices and optimised for jet flavour identification, are used in a multidimensional template fit to measure the fractions of these dijet flavour states as functions of the leading jet transverse momentum in the range 40 GeV to 500 GeV and jet rapidity |y|<2.1. The fit results agree with the predictions of leading- and next-to-leading-order calculations, with the exception of the dijet fraction composed of bottom and light flavour jets, which is underestimated by all models at large transverse jet momenta. The ability to identify jets containing two b-hadrons, originating from e.g. gluon splitting, is demonstrated. The difference between bottom jet production rates in leading and subleading jets is consistent with the next-to-leading-order predictions
- …