1,121 research outputs found
The Higgs System in and Beyond the Standard Model
After the discovery of the Higgs boson particle on the 4th of July of 2012 at
the Large Hadron Collider, sited at the european CERN laboratory, we are
entering in a fascinating period for Particle Physics where both theorists and
experimentalists are devoted to fully understand the features of this new
particle and the possible consequences for High Energy Physics of the Higgs
system both within and beyond the Standard Model of fundamental particle
interactions. This paper is a summary of the lectures given at the third IDPASC
school (Santiago de Compostela, Feb. 2013, Spain) addressed to PhD students,
and contains a short introduction to the main basic aspects of the Higgs boson
particle in and beyond the Standard Model.Comment: 62 pages, 31 figures, Lectures of the IDPASC School at Santiago de
Compostela, Spain, February 201
Gauge Theories and the Standard Model
This chapter, Chaps. 3 and 4 present a self-contained introduction to the Standard Model of fundamental interactions, which describes in the unified framework of gauge quantum field theories all of the fundamental forces of nature but gravity: the strong, weak, and electromagnetic interactions. This set of chapters thus provides both an introduction to the Standard Model, and to quantum field theory at an intermediate level. The union of the three chapters can be taken as a masters\u2019 level course reference, and it requires as a prerequisite an elementary knowledge of quantum field theory, at the level of many introductory textbooks, such as Vol. 1 of Aitchison-Hey, or, at a somewhat more advanced level, Maggiore. The treatment is subdivided into three parts, each corresponding to an individual chapter, with more advanced field theory topics introduced along the way as needed. Specifically, this chapter presents the general structure of the Standard Model, its field content, and symmetry structure. This involves an introduction to non-abelian gauge theories both at the classical and quantum level. Also, it involves a discussion of spontaneous symmetry breaking and the Higgs mechanism, that play a crucial role in the architecture of the Standard Model, and their interplay with the quantization of gauge theories. Chapter 3 then presents the electroweak sector of the Standard Model. This requires introducing the concepts of CP violation and mixing, and of radiative corrections. Finally, Chap. 4 presents the strong sector of the theory, which requires a more detailed treatment of renormalization and the renormalization group
True Neutrality as a New Type of Flavour
A classification of leptonic currents with respect to C-operation requires
the separation of elementary particles into the two classes of vector C-even
and axial-vector C-odd character. Their nature has been created so that to each
type of lepton corresponds a kind of neutrino. Such pairs are united in
families of a different C-parity. Unlike the neutrino of a vector type, any
C-noninvariant Dirac neutrino must have his Majorana neutrino. They constitute
the purely neutrino families. We discuss the nature of a corresponding
mechanism responsible for the availability in all types of axial-vector
particles of a kind of flavour which distinguishes each of them from others by
a true charge characterized by a quantum number conserved at the interactions
between the C-odd fermion and the field of emission of the corresponding types
of gauge bosons. This regularity expresses the unidenticality of truly neutral
neutrino and antineutrino, confirming that an internal symmetry of a
C-noninvariant particle is described by an axial-vector space. Thereby, a true
flavour together with the earlier known lepton flavour predicts the existence
of leptonic strings and their birth in single and double beta decays as a unity
of flavour and gauge symmetry laws. Such a unified principle explains the
availability of a flavour symmetrical mode of neutrino oscillations.Comment: 19 pages, LaTex, Published version in IJT
Flavour Physics and CP Violation in the Standard Model and Beyond
We present the invited lectures given at the Third IDPASC School which took
place in Santiago de Compostela in January 2013. The students attending the
school had very different backgrounds, some of them were doing their Ph.D. in
experimental particle physics, others in theory. As a result, and in order to
make the lectures useful for most of the students, we focused on basic topics
of broad interest, avoiding the more technical aspects of Flavour Physics and
CP Violation. We make a brief review of the Standard Model, paying special
attention to the generation of fermion masses and mixing, as well as to CP
violation. We describe some of the simplest extensions of the SM, emphasising
novel flavour aspects which arise in their framework.Comment: Invited talk at the Third IDPASC School 2013, January 21st - February
2nd 2013, Santiago de Compostela, Galiza, Spain; 36 pages, 8 figures, 2
tables; version with few misprints correcte
A Statistical Method for Reassociating Human Tali and Calcanei from a Commingled Context.
In a commingled context, assessing that a talus and a calcaneus correspond to the same individual could become a primary step for accurately sorting human remains. For this purpose, the lengths and widths of the trochlea, posterior calcaneal articular surface, and posterior talar articular surface were measured in 197 individuals (105 males, 92 females) from the Athens Collection. A total of 12 highly accurate equations for reassociating tali and calcanei were developed, using simple and multiple linear regression analysis and they were found to be suitable for sorting commingled human remains. Bilateral asymmetry and sex did not have an effect on the accuracy of the method
Historical geography II: traces remain
The second report in this series turns to focus on the trace in relation to life-writing and biography in historical geography and beyond. Through attention to tracing journeys, located moments and listening to the presence of ghosts (Ogborn, 2005), this report seeks to highlight the range of different ways in which historical geographers have explored lives, deaths, and their transient traces through varied biographical terrains. Continuing to draw attention in historical geography to the darkest of histories, this piece will pivot on moments of discovering the dead to showcase the nuanced ways in which historical geography is opening doors into uncharted lives and unspoken histories
Anthropic solution to the magnetic muon anomaly: the charged see-saw
We present models of new physics that can explain the muon g-2 anomaly in
accord with with the assumption that the only scalar existing at the weak scale
is the Higgs, as suggested by anthropic selection. Such models are dubbed
"charged see-saw" because the muon mass term is mediated by heavy leptons. The
electroweak contribution to the g-2 gets modified by order one factors, giving
an anomaly of the same order as the observed hint, which is strongly correlated
with a modification of the Higgs coupling to the muon.Comment: 21 pages, many equations despite the first word in the title. v3:
loop function G_WN corrected, conclusions unchange
Bulk Axions, Brane Back-reaction and Fluxes
Extra-dimensional models can involve bulk pseudo-Goldstone bosons (pGBs)
whose shift symmetry is explicitly broken only by physics localized on branes.
Reliable calculation of their low-energy potential is often difficult because
it requires details of the stabilization of the extra dimensions. In rugby ball
solutions, for which two compact extra dimensions are stabilized in the
presence of only positive-tension brane sources, the effects of brane
back-reaction can be computed explicitly. This allows the calculation of the
shape of the low-energy pGB potential and response of the extra dimensional
geometry as a function of the perturbing brane properties. If the
pGB-dependence is a small part of the total brane tension a very general
analysis is possible, permitting an exploration of how the system responds to
frustration when the two branes disagree on what the proper scalar vacuum
should be. We show how the low-energy potential is given by the sum of brane
tensions (in agreement with common lore) when only the brane tensions couple to
the pGB. We also show how a direct brane coupling to the flux stabilizing the
extra dimensions corrects this result in a way that does not simply amount to
the contribution of the flux to the brane tensions. We calculate the mass of
the would-be zero mode, and briefly describe several potential applications,
including a brane realization of `natural inflation,' and a dynamical mechanism
for suppressing the couplings of the pGB to matter localized on the branes.
Since the scalar can be light enough to be relevant to precision tests of
gravity (in a technically natural way) this mechanism can be relevant to
evading phenomenological bounds.Comment: 36 pages, JHEP styl
Monopoles and Holography
We present a holographic theory in AdS_4 whose zero temperature ground state
develops a crystal structure, spontaneously breaking translational symmetry.
The crystal is induced by a background magnetic field, but requires no chemical
potential. This lattice arises from the existence of 't Hooft-Polyakov monopole
solitons in the bulk which condense to form a classical object known as a
monopole wall. In the infra-red, the magnetic field is screened and there is an
emergent SU(2) global symmetry.Comment: 33 pages, 16 figures; v2: ref adde
P-odd and CP-odd Four-Quark Contributions to Neutron EDM
In a class of beyond-standard-model theories, CP-odd observables, such as the
neutron electric dipole moment, receive significant contributions from
flavor-neutral P-odd and CP-odd four-quark operators. However, considerable
uncertainties exist in the hadronic matrix elements of these operators strongly
affecting the experimental constraints on CP-violating parameters in the
theories. Here we study their hadronic matrix elements in combined chiral
perturbation theory and nucleon models. We first classify the operators in
chiral representations and present the leading-order QCD evolutions. We then
match the four-quark operators to the corresponding ones in chiral hadronic
theory, finding symmetry relations among the matrix elements. Although this
makes lattice QCD calculations feasible, we choose to estimate the
non-perturbative matching coefficients in simple quark models. We finally
compare the results for the neutron electric dipole moment and P-odd and CP-odd
pion-nucleon couplings with the previous studies using naive factorization and
QCD sum rules. Our study shall provide valuable insights on the present
hadronic physics uncertainties in these observables.Comment: 40 pages, 7 figures. This is the final version. A discussion of the
uncertainty of the calculation is adde
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