Recently, new imaging modalities based on the detection of weak phase perturbations effects, among which are phase contrast and diffraction imaging, have been developed by several researchers. Due to ...their high sensitivity to weakly absorbing details, these techniques seem to be very promising for applications in the medical field. On the other hand, digital radiology is undergoing a wide diffusion, and its benefits are presently very well understood. Up to now, however, the strong pixel size constraints associated with phase contrast pattern detection limited the possibility of exploiting the advantages of phase contrast in digital radiology applications. In this paper, an innovative setup capable of removing the pixel size constraints, and thus opening the way to low dose digital phase contrast imaging, is described. Furthermore, we introduce an imaging technique based on the detection of radiation scattered at small angles: the information extracted from the sample is increased at no dose expense. We believe that several radiological fields, mammography being the first important example, may benefit from the herein described innovative imaging techniques.
Phase contrast x-ray imaging is a powerful technique for the detection of low-contrast details in weakly absorbing objects. This method is of possible relevance in the field of diagnostic radiology. ...In fact, imaging low-contrast details within soft tissue does not give satisfactory results in conventional x-ray absorption radiology, mammography being a typical example. Nevertheless, up to now all applications of the phase contrast technique, carried out on thin samples, have required radiation doses substantially higher than those delivered in conventional radiological examinations. To demonstrate the applicability of the method to mammography we produced phase contrast images of objects a few centimetres thick while delivering radiation doses lower than or comparable to doses needed in standard mammographic examinations (typically approximately 1 mGy mean glandular dose (MGD)). We show images of a custom mammographic phantom and of two specimens of human breast tissue obtained at the SYRMEP bending magnet beamline at Elettra, the Trieste synchrotron radiation facility. The introduction of an intensifier screen enabled us to obtain phase contrast images of these thick samples with radiation doses comparable to those used in mammography. Low absorbing details such as 50 microm thick nylon wires or thin calcium deposits (approximately 50 microm) within breast tissue, invisible with conventional techniques, are detected by means of the proposed method. We also find that the use of a bending magnet radiation source relaxes the previously reported requirements on source size for phase contrast imaging. Finally, the consistency of the results has been checked by theoretical simulations carried out for the purposes of this experiment.
The Physics of the B Factories Bevan, Adrian; Golob, Bostjan; Mannel, Thomas ...
The European physical journal. C, Particles and fields,
March 2015, Letnik:
74, Številka:
11
eBook, Journal Article
Recenzirano
Odprti dostop
This work is on the Physics of the B Factories. Part A of this book contains a brief description of the SLAC and KEK B Factories as well as their detectors, BaBar and Belle, and data taking related ...issues. Part B discusses tools and methods used by the experiments in order to obtain results. The results themselves can be found in Part C.
Electroweak measurements performed with data taken at the electron–positron collider LEP at CERN from 1995 to 2000 are reported. The combined data set considered in this report corresponds to a total ...luminosity of about 3 fb−1 collected by the four LEP experiments ALEPH, DELPHI, L3 and OPAL, at centre-of-mass energies ranging from 130 GeV to 209 GeV.
Combining the published results of the four LEP experiments, the measurements include total and differential cross-sections in photon-pair, fermion-pair and four-fermion production, the latter resulting from both double-resonant WW and ZZ production as well as singly resonant production. Total and differential cross-sections are measured precisely, providing a stringent test of the Standard Model at centre-of-mass energies never explored before in electron–positron collisions. Final-state interaction effects in four-fermion production, such as those arising from colour reconnection and Bose–Einstein correlations between the two W decay systems arising in WW production, are searched for and upper limits on the strength of possible effects are obtained. The data are used to determine fundamental properties of the W boson and the electroweak theory. Among others, the mass and width of the W boson, mW and ΓW, the branching fraction of W decays to hadrons, B(W→had), and the trilinear gauge-boson self-couplings g1Z, κγ and λγ are determined to be: mW=80.376±0.033GeVΓW=2.195±0.083GeVB(W→had)=67.41±0.27%g1Z=0.984−0.020+0.018κγ=0.982±0.042λγ=−0.022±0.019.
The BaBar detector: Upgrades, operation and performance Couderc, F.; Prudent, X.; Groysman, Y. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2013, Letnik:
729, Številka:
C
Journal Article
Recenzirano
Odprti dostop
The BaBar detector operated successfully at the PEP-II asymmetric e+e− collider at the SLAC National Accelerator Laboratory from 1999 to 2008. This report covers upgrades, operation, and performance ...of the collider and the detector systems, as well as the trigger, online and offline computing, and aspects of event reconstruction since the beginning of data taking.
We report on the final electroweak measurements performed with data taken at the Z resonance by the experiments operating at the electron–positron colliders SLC and LEP. The data consist of 17 ...million Z decays accumulated by the ALEPH, DELPHI, L3 and OPAL experiments at LEP, and 600 thousand Z decays by the SLD experiment using a polarised beam at SLC. The measurements include cross-sections, forward–backward asymmetries and polarised asymmetries. The mass and width of the Z boson,
m
Z
and
Γ
Z
, and its couplings to fermions, for example the
ρ
parameter and the effective electroweak mixing angle for leptons, are precisely measured:
m
Z
=
91.1875
±
0.0021
GeV
,
Γ
Z
=
2.4952
±
0.0023
GeV
,
ρ
ℓ
=
1.0050
±
0.0010
,
sin
2
θ
eff
lept
=
0.23153
±
0.00016
.
The number of light neutrino species is determined to be
2.9840
±
0.0082
, in agreement with the three observed generations of fundamental fermions.
The results are compared to the predictions of the Standard Model (SM). At the Z-pole, electroweak radiative corrections beyond the running of the QED and QCD coupling constants are observed with a significance of five standard deviations, and in agreement with the Standard Model. Of the many Z-pole measurements, the forward–backward asymmetry in b-quark production shows the largest difference with respect to its SM expectation, at the level of 2.8 standard deviations.
Through radiative corrections evaluated in the framework of the Standard Model, the Z-pole data are also used to predict the mass of the top quark,
m
t
=
173
-
10
+
13
GeV
, and the mass of the W boson,
m
W
=
80.363
±
0.032
GeV
. These indirect constraints are compared to the direct measurements, providing a stringent test of the SM. Using in addition the direct measurements of
m
t
and
m
W
, the mass of the as yet unobserved SM Higgs boson is predicted with a relative uncertainty of about 50% and found to be less than
285
GeV
at 95% confidence level.
The Physics of the B Factories Golob, Bostjan; Mannel, Thomas; Bevan, Adrian
The European physical journal. C, Particles and fields,
March 2015, Letnik:
74, Številka:
11
eBook, Journal Article
PDF
