We introduce a novel anomaly search method based on (i) jet tagging to select interesting events, which are less likely to be produced by background processes; (ii) comparison of the untagged and ...tagged samples to single out features (such as bumps produced by the decay of new particles) in the latter. We demonstrate the usefulness of this method by applying it to a final state with two massive boosted jets: for the new physics benchmarks considered, the signal significance increases an order of magnitude, up to a factor of 40. We compare to other anomaly detection methods in the literature and discuss possible generalisations.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We discuss quantum entanglement in top pair production at the LHC. Near the
t
t
¯
threshold, entanglement observables are enhanced by suppressing the contribution of
q
q
¯
subprocesses, which is ...achieved by a simple cut on the velocity of the
t
t
¯
system in the laboratory frame. Furthermore, we design new observables that directly measure the relevant combinations of
t
t
¯
spin correlation coefficients involved in the measurement of entanglement and Bell inequalities. As a result, the statistical sensitivity is enhanced, up to a factor of 7 for Bell inequalities near threshold.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We address the modeling dependence of jet taggers built using the method of mass unspecific supervised tagging, by using two different parton showering and hadronisation schemes. We find that the ...modeling dependence of the results – estimated by using different schemes in the design of the taggers and applying them to the same type of data – is rather small, even if the jet substructure varies significantly between the two schemes. These results add great value to the use of generic supervised taggers for new physics searches.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Double perovskite La1.8Sr0.2CoFeO5+δ (DP-LSCF) is prepared by a modified sol-gel method and investigated as a cathode material for intermediate temperature solid oxide fuel cells (IT-SOFCs, ...600–850 °C). The compound is characterised by a variety of techniques, including TG/DTA, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and SEM-EDS. The formation of the double perovskite structure with rhombohedral symmetry after its calcination at 1000 °C for 6 h is revealed by X-ray diffraction. Excellent chemical compatibility with a Ce0.9Gd0.1O1.95 (GDC) electrolyte is found. The double perovskite structure is confirmed by Raman and X-ray photoelectron spectroscopy. The partial substitution of Fe cations at the Co site affects the physical-chemical properties of DP-LSCF. Compared with other double perovskite materials based on Co, DP-LSCF shows a lower thermal expansion coefficient (19.4 × 10−6 K−1). The compound exhibits semiconductor behaviour and an area specific resistance of 0.42 Ω cm2 at 800 °C when GDC is employed as the electrolyte. These results suggest that DP-LSCF is a promising cathode material for IT-SOFC applications.
•LSFC studied as IT-SOFC potential electrode.•TEC ≈ GDC-TEC.•Viable electrochemical properties.
Stealth multiboson signals Aguilar-Saavedra, J. A.
The European physical journal. C, Particles and fields,
10/2017, Letnik:
77, Številka:
10
Journal Article
Recenzirano
Odprti dostop
We introduce the ‘stealth bosons’
S
, light boosted particles with a decay
S
→
A
A
→
q
q
¯
q
q
¯
into two daughter bosons
A
, which subsequently decay into four quarks that are reconstructed as a ...single fat jet. Variables that measure the two-pronged structure of fat jets, which are used for diboson resonance searches in hadronic or semi-leptonic final states, classify the jets produced in stealth boson decays as QCD-like – actually, for these variables they may seem more background-like than the QCD background itself. The number of tracks in those jets can also be, on average, much higher than for the fat jets arising from the hadronic decay of boosted
W
and
Z
bosons. Therefore, these elusive particles are hard to spot in standard searches. Heavy resonances decaying into two such stealth bosons, or one plus a
W
/
Z
boson, could offer an explanation for the recurrent small excesses found in hadronic diboson resonance searches near an invariant mass of 2 TeV.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Multiphoton signals of a (96 GeV?) stealth boson Aguilar-Saavedra, J. A.; Joaquim, F. R.
The European physical journal. C, Particles and fields,
05/2020, Letnik:
80, Številka:
5
Journal Article
Recenzirano
Odprti dostop
Cascade decays of new scalars into final states with multiple photons and possibly quarks may lead to distinctive experimental signatures at high-energy colliders. Such signals are even more striking ...if the scalars are highly boosted, as when produced from the decay of a much heavier resonance. We study this type of events within the framework of the minimal stealth boson model, an anomaly-free
U
(
1
)
Y
′
extension of the Standard Model with two complex scalar singlets. It is shown that, while those signals may have cross sections that might render them observable with LHC Run 2 data, they have little experimental coverage. We also establish a connection with a CMS excess observed in searches for new scalars decaying into diphoton final states near 96 GeV. In particular, we conclude that the predicted multiphoton signatures are compatible with such excess.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A generic anti-QCD jet tagger Aguilar-Saavedra, J. A.; Collins, Jack; Mishra, Rashmish K.
The journal of high energy physics,
11/2017, Letnik:
2017, Številka:
11
Journal Article
Recenzirano
Odprti dostop
A
bstract
New particles beyond the Standard Model might be produced with a very high boost, for instance if they result from the decay of a heavier particle. If the former decay hadronically, then ...their signature is a single massive fat jet which is difficult to separate from QCD backgrounds. Jet substructure and machine learning techniques allow for the discrimination of many specific boosted objects from QCD, but the scope of possibilities is very large, and a suite of dedicated taggers may not be able to cover every possibility — in addition to making experimental searches cumbersome. In this paper we describe a generic model-independent tagger that is able to discriminate a wide variety of hadronic boosted objects from QCD jets using
N
-subjettiness variables, with a significance improvement varying between 2 and 8. This is in addition to any improvement that might come from a cut on jet mass. Such a tagger can be used in model-independent searches for new physics yielding fat jets. We also show how such a tagger can be applied to signatures over a wide range of jet masses without sculpting the background distributions, allowing to search for new physics as bumps on jet mass distributions.
•A review on acaricide activity against ticks of plant products and secondary compounds was done.•Mortalities (5–100%) against the Rhipicephalus, Amblyomma, Dermacentor, Hyalomma and Argas genera ...were reported.•The families Lamiaceae, Fabaceae, Asteraceae, Piperaceae, Verbenaceae, and Poaceae are evaluated mainly.•Thymol, carvacrol, 1,8-cineol, n-hexanal, nicotine and sulfides are responsible for the acaricidal activity.•Plant metabolites could be used as an alternative control against susceptible or resistant ticks to commercial acaricides.
The present review documents the results of studies evaluating the acaricidal activity of different plant products and secondary metabolites against ticks that are resistant and susceptible to conventional acaricides. Studies published from 1998 to 2016 were included. The acaricidal activity of plant extracts, essential oils and secondary compounds from plants have been evaluated using bioassays with ticks in the larval and adult stages. There is variable effectiveness according to the species of plant and the concentrations used, with observed mortalities ranging from 5 to 100% against the Rhipicephalus (Boophilus), Amblyomma, Dermacentor, Hyalomma, and Argas genera. A number of plants have been reported to cause high mortalities and/or affect the reproductive capacity of ticks in the adult phase. In the majority of these trials, the main species of plants evaluated correspond to the families Lamiaceae, Fabaceae, Asteraceae, Piperaceae, Verbenaceae, and Poaceae. Different secondary metabolites such as thymol, carvacrol, 1,8-cineol and n-hexanal, have been found to be primarily responsible for the acaricidal activity of different essential oils against different species of ticks, while nicotine, dibenzyldisulfide and dibenzyltrisulfide have been evaluated for plant extracts. Only thymol, carvacrol and 1,8-cineol have been evaluated for acaricidal activity under in vivo conditions. The information in the present review allows the conclusion that the secondary metabolites contained in plant products could be used as an alternative for the control of ticks that are susceptible or resistant to commercial acaricides.
Jet tagging has become an essential tool for new physics searches at the high-energy frontier. For jets that contain energetic charged leptons we introduce Feature Extended Supervised Tagging (FEST) ...which, in addition to jet substructure, considers the features of the charged lepton within the jet. With this method we build dedicated taggers to discriminate among boosted
H
→
ℓ
ν
q
q
¯
,
t
→
ℓ
ν
b
, and QCD jets (with
ℓ
an electron or muon). The taggers have an impressive performance, allowing for overall light jet rejection factors of
10
4
-
10
5
, for top quark/Higgs boson efficiencies of 0.5. The taggers are also excellent in the discrimination of Higgs bosons from top quarks and vice versa, for example rejecting top quarks by factors of 100–300 for Higgs boson efficiencies of 0.5. We demonstrate the potential of these taggers to improve the sensitivity to new physics by using as example a search for a new
Z
′
boson decaying into
ZH
, in the fully-hadronic final state.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We consider a pair of unstable fermions in a spin-entangled state. After the decay of one fermion, a spin measurement is performed on the surviving partner, with a Stern-Gerlach experiment or ...similar. The measurement not only projects the spin of the surviving fermion, but is also physically equivalent to a spin projection for the decayed one — even when it no longer exists. This post-selection effect would be experimentally accessible using muon pairs in a maximally-entangled state, produced either in the decay of a scalar particle, or in e+e− collisions at wide angles.
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