Boosting H→bb¯ with machine learning Lin, Joshua; Freytsis, Marat; Moult, Ian ...
The journal of high energy physics,
16/10, Letnik:
2018, Številka:
10
Journal Article
Recenzirano
Odprti dostop
A
bstract
High-
p
T
Higgs production at hadron colliders provides a direct probe of the internal structure of the
gg
→
H
loop with the
H
→
b
b
¯
decay offering the most statistics due to the large ...branching ratio. Despite the overwhelming QCD background, recent advances in jet substructure have put the observation of the
gg
→
H
→
b
b
¯
channel at the LHC within the realm of possibility. In order to enhance the sensitivity to this process, we develop a two-stream convolutional neural network, with one stream acting on jet information and one using global event properties. The neural network significantly increases the discovery potential of a Higgs signal, both for high-
p
T
Standard Model production as well for possible beyond the Standard Model contributions. Unlike most studies for boosted hadronically decaying massive particles, the boosted Higgs search is unique because double
b
-tagging rejects nearly all background processes that do not have two hard prongs. In this context — which goes beyond state-of-the-art two-prong tagging — the network is studied to identify the origin of the additional information leading to the increased significance. The procedures described here are also applicable to related final states where they can be used to identify additional sources of discrimination power that are not being exploited by current techniques.
In previous work, we developed a deep neural network classifier that only relies on phase-space information to obtain a catalog of accreted stars based on the second data release of Gaia (DR2). In ...this paper, we apply two clustering algorithms to identify velocity substructure within this catalog. We focus on the subset of stars with line-of-sight velocity measurements that fall in the range of Galactocentric radii and vertical distances . Known structures such as Gaia Enceladus and the Helmi stream are identified. The largest previously unknown structure, Nyx, is a vast stream consisting of at least 200 stars in the region of interest. This study displays the power of the machine-learning approach by not only successfully identifying known features but also discovering new kinematic structures that may shed light on the merger history of the Milky Way.
We use functional methods to compute one-loop effects in Heavy Quark Effective Theory. The covariant derivative expansion technique facilitates the efficient extraction of matching coefficients and ...renormalization group evolution equations. This paper pro- vides the first demonstration that such calculations can be performed through the algebraic evaluation of the path integral for the class of effective field theories that are (i) constructed using a non-trivial one-to-many mode decomposition of the UV theory, and (ii) valid for non-relativistic kinematics. We discuss the interplay between operators that appear at intermediate steps and the constraints imposed by the residual Lorentz symmetry that is encoded as reparameterization invariance within the effective description. The tools presented here provide a systematic approach for computing corrections to higher order in the heavy mass expansion; precision applications include predictions for experimental data and connections to theoretical tests via lattice QCD. A set of pedagogical appendices comprehensively reviews modern approaches to performing functional calculations algebraically, and derives contributions from a term with open covariant derivatives for the first time.
A
bstract
We consider a twin WIMP scenario whose twin sector contains a full dark copy of the SM hadrons, where the lightest twin particles are twin pions. By analogy to the standard WIMP paradigm, ...the dark matter (DM) freezes out through twin electroweak interactions, and annihilates into a dark shower of light twin hadrons. These are either stable or decay predominantly to standard model (SM) photons. We show that this ‘hadrosymmetric’ scenario can be consistent with all applicable astrophysical, cosmological and collider constraints. In order to decay the twin hadrons before the big-bang nucleosynthesis epoch, an additional portal between the SM and twin sector is required. In most cases we find this additional mediator is within reach of either the LHC or future intensity frontier experiments. Furthermore, we conduct simulations of the dark shower and consequent photon spectra. We find that fits of these spectra to the claimed galactic center gamma-ray excess seen by
Fermi
-LAT non-trivially coincide with regions of parameter space that both successfully generate the observed DM abundance and exhibit minimal fine-tuning.
QED plasma and magnetars Freytsis, Marat; Gralla, Samuel E.
Journal of cosmology and astroparticle physics,
05/2016, Letnik:
2016, Številka:
5
Journal Article
Recenzirano
Odprti dostop
Magnetars are surrounded by diffuse plasma in magnetic field strengths well above the quantum electrodynamic critical value. We derive equations of ''quantum force-free electrodynamics'' for this ...plasma using effective field theory arguments. We argue that quantum effects do not modify the large scale structure of the magnetosphere, and in particular that the spin-down rate does not deviate significantly from the classical result. We provide definite evolution equations that can be used to explore potentially important small-scale corrections, such as shock formation, which has been proposed as a mechanism for both burst and quiescent emission from magnetars.
Toward extracting γ from B→DK without binning Backus, Jeffrey V.; Freytsis, Marat; Grossman, Yuval ...
The European physical journal. C, Particles and fields,
09/2023, Letnik:
83, Številka:
9
Journal Article
Recenzirano
Odprti dostop
B
±
→
D
K
±
transitions are known to provide theoretically clean information about the CKM angle
γ
, with the most precise available methods exploiting the cascade decay of the neutral
D
into
CP
...self-conjugate states. Such analyses currently require binning in the
D
decay Dalitz plot, while a recently proposed method replaces this binning with the truncation of a Fourier series expansion. In this paper, we present a proof of principle of a novel alternative to these two methods, in which no approximations at the level of the data representation are required. In particular, our new strategy makes no assumptions about the amplitude and strong phase variation over the Dalitz plot. This comes at the cost of a degree of ambiguity in the choice of test statistic quantifying the compatibility of the data with a given value of
γ
, with improved choices of test statistic yielding higher sensitivity. While our current proof-of-principle implementation does not demonstrate optimal sensitivity to
γ
, its conceptually novel approach opens the door to new strategies for
γ
extraction. More studies are required to see if these can be competitive with the existing methods.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
$$B^\pm \rightarrow DK^\pm $$
B
±
→
D
K
±
transitions are known to provide theoretically clean information about the CKM angle
$$\gamma $$
γ
, with the most precise available methods ...exploiting the cascade decay of the neutral
D
into
CP
self-conjugate states. Such analyses currently require binning in the
D
decay Dalitz plot, while a recently proposed method replaces this binning with the truncation of a Fourier series expansion. In this paper, we present a proof of principle of a novel alternative to these two methods, in which no approximations at the level of the data representation are required. In particular, our new strategy makes no assumptions about the amplitude and strong phase variation over the Dalitz plot. This comes at the cost of a degree of ambiguity in the choice of test statistic quantifying the compatibility of the data with a given value of
$$\gamma $$
γ
, with improved choices of test statistic yielding higher sensitivity. While our current proof-of-principle implementation does not demonstrate optimal sensitivity to
$$\gamma $$
γ
, its conceptually novel approach opens the door to new strategies for
$$\gamma $$
γ
extraction. More studies are required to see if these can be competitive with the existing methods.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A
bstract
High-
p
T
Higgs production at hadron colliders provides a direct probe of the internal structure of the
gg
→
H
loop with the
$$ H\to b\overline{b} $$
H
→
b
b
¯
decay offering the most ...statistics due to the large branching ratio. Despite the overwhelming QCD background, recent advances in jet substructure have put the observation of the
$$ gg\to H\to b\overline{b} $$
gg
→
H
→
b
b
¯
channel at the LHC within the realm of possibility. In order to enhance the sensitivity to this process, we develop a two-stream convolutional neural network, with one stream acting on jet information and one using global event properties. The neural network significantly increases the discovery potential of a Higgs signal, both for high-
p
T
Standard Model production as well for possible beyond the Standard Model contributions. Unlike most studies for boosted hadronically decaying massive particles, the boosted Higgs search is unique because double
b
-tagging rejects nearly all background processes that do not have two hard prongs. In this context — which goes beyond state-of-the-art two-prong tagging — the network is studied to identify the origin of the additional information leading to the increased significance. The procedures described here are also applicable to related final states where they can be used to identify additional sources of discrimination power that are not being exploited by current techniques.
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