765 research outputs found
Benzo(a)pyrene air concentrations and emission inventory in Lombardy region, Italy
Three years of particle phase B(a)P air concentration measurements in 13 sites in Lombardy (Italy) and a detailed emission inventory at the municipal scale for the whole region were used to infer the contribution of different sources to B(a)P atmospheric levels. The analyses of the weekly and monthly profiles of B(a)P concentrations, the cluster analysis and the comparison between the B(a)P/PM10 ratios in ambient air and in the emissions allowed identifying wood burning in small residential appliances as the key source for all the sites, except for those located in Milan. The highest values of the average B(a)P concentrations were not found in the wider urban areas, where in general the highest PM10 levels were registered. Regarding the seasonal variability, a marked reduction of both B(a)P concentrations and B(a)P/PM10 ratios was observed in the summer season. The cluster analysis of PM10 and B(a)P concentrations showed that the two pollutants tend to have a separate pattern; moreover the cluster analysis of B(a)P/PM10 ratios showed that the trend of this ratio split the stations depending on their location: plain area, piedmont and valley zones, and mountain sites. The dominance of the wood combustion highlighted by the emission inventory, originating from the residential sector and from pizzerias in the city of Milan, is consistent with the findings of other studies based on a source apportionment approach or air quality modeling, although some patterns of ambient B(a)P concentrations in one site were not adequately explained by the emission sources included in the emission inventory
Spatial and temporal variability of carbonaceous aerosols: assessing the impact of biomass burning in the urban environment
Biomass burning (BB) is a significant source of atmospheric particles in many parts of the world. Whereas many studies have demonstrated the importance of BB emissions in central and northern Europe, especially in rural areas, its impact in urban air quality of southern European countries has been sparsely investigated. In this study, highly time resolved multi-wavelength absorption coefficients together with levoglucosan (BB tracer) mass concentrations were combined to apportion carbonaceous aerosol sources. The Aethalometer model takes advantage of the different spectral behaviour of BB and fossil fuel (FF) combustion aerosols. The model was found to be more sensitive to the assumed value of the aerosol Ångström exponent (AAE) for FF (AAEff) than to the AAE for BB (AAEbb). As result of various sensitivity tests the model was optimized with AAEff = 1.1 and AAEbb = 2. The Aethalometer model and levoglucosan tracer estimates were in good agreement. The Aethalometer model was further applied to data from three sites in Granada urban area to evaluate the spatial variation of CMff and CMbb (carbonaceous matter from FF or BB origin, respectively) concentrations within the city. The results showed that CMbb was lower in the city centre while it has an unexpected profound impact on the CM levels measured in the suburbs (about 40%). Analysis of BB tracers with respect to wind speed suggested that BB was dominated by sources outside the city, to the west in a rural area. Distinguishing whether it corresponds to agricultural waste burning or with biomass burning for domestic heating was not possible. This study also shows that although traffic restrictions measures contribute to reduce carbonaceous concentrations, the extent of the reduction is very local. Other sources such as BB, which can contribute to CM as much as traffic emissions, should be targeted to reduce air pollution.This research was partially supported by the Andalusia Regional Government through projects P10-RNM-6299 and P12-RNM-2409, by the Spanish Ministry of Economy and Competitiveness and FEDER through project CGL2013_45410-R; by EUREKA and the Slovenian Ministry of Economic Development and Technology grants (Eurostars grant E!4825 FC Aeth, JR-KROP grant 3211-11-000519); and by European Union's Horizon 2020 Research and Innovation Programme under grant agreement No. 654109, ACTRIS-2. The authors would like to thank Air Quality Service from Junta de Andalucía (Consejería de Medio Ambiente y Ordenación del Territorio) and Vicerrectorado de Política Científica e Investigación from the University of Granada for their support in the installation of the Aethalometer at PC and GV, respectively.G. Titos was partially funded by Programa del Plan Propio de Investigación “Contrato Puente” of the University of Granada and by the Spanish Ministry of Economy and Competitiveness under postdoctoral program Juan de la Cierva – Formación (FJCI-2014-20819)
Observation of two new baryon resonances
Two structures are observed close to the kinematic threshold in the mass spectrum in a sample of proton-proton collision data, corresponding
to an integrated luminosity of 3.0 fb recorded by the LHCb experiment.
In the quark model, two baryonic resonances with quark content are
expected in this mass region: the spin-parity and
states, denoted and .
Interpreting the structures as these resonances, we measure the mass
differences and the width of the heavier state to be
MeV,
MeV,
MeV, where the first and second
uncertainties are statistical and systematic, respectively. The width of the
lighter state is consistent with zero, and we place an upper limit of
MeV at 95% confidence level. Relative
production rates of these states are also reported.Comment: 17 pages, 2 figure
Observation of associated production of a boson with a meson in the~forward region
A search for associated production of a boson with an open charm meson is
presented using a data sample, corresponding to an integrated luminosity of
of proton--proton collisions at a centre-of-mass energy
of 7\,TeV, collected by the LHCb experiment. %% Seven candidate events for
associated production of a boson with a meson and four candidate
events for a boson with a meson are observed with a combined
significance of 5.1standard deviations. The production cross-sections in the
forward region are measured to be where the first uncertainty is statistical and the
second systematic.Comment: 18 pages, 2 figure
Measurements of the , , meson and baryon lifetimes
Measurements of -hadron lifetimes are reported using collision data,
corresponding to an integrated luminosity of 1.0fb, collected by the
LHCb detector at a centre-of-mass energy of Tev. Using the exclusive decays
, , ,
and the average decay
times in these modes are measured to be = 0.004 0.003 ps, =
0.006 0.004 ps, = 0.013
0.005 ps, = 0.027
0.006 ps and = 0.011
0.005 ps, where the first uncertainty is statistical and the second is
systematic. These represent the most precise lifetime measurements in these
decay modes. In addition, ratios of these lifetimes, and the ratio of the
decay-width difference, , to the average width, , in
the system, , are
reported. All quantities are found to be consistent with Standard Model
expectations.Comment: 28 pages, 4 figures. Updated reference
First observation and amplitude analysis of the decay
The decay is observed in a data sample
corresponding to of collision data recorded by the LHCb
experiment during 2011 and 2012. Its branching fraction is measured to be
where the uncertainties are statistical, systematic and from
the branching fraction of the normalisation channel , respectively. An amplitude analysis of the resonant
structure of the decay is used to measure the
contributions from quasi-two-body ,
, and
decays, as well as from nonresonant sources. The
resonance is determined to have spin~1.Comment: 39 pages, 10 figures, submitted to Phys. Rev. D. Updated following
erratum 10.1103/PhysRevD.93.11990
Study of and decays and determination of the CKM angle
We report a study of the suppressed and favored
decays, where the neutral meson is detected
through its decays to the and CP-even and
final states. The measurement is carried out using a proton-proton
collision data sample collected by the LHCb experiment, corresponding to an
integrated luminosity of 3.0~fb. We observe the first significant
signals in the CP-even final states of the meson for both the suppressed
and favored modes, as well as
in the doubly Cabibbo-suppressed final state of the decay. Evidence for the ADS suppressed decay , with , is also presented. From the observed
yields in the , and their
charge conjugate decay modes, we measure the value of the weak phase to be
. This is one of the most precise
single-measurement determinations of to date.Comment: 22 pages, 9 figures; All figures and tables, along with any
supplementary material and additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2015-020.htm
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