Archivi tag: particle physics

Neutrinos in Astro- and Particle Physics

The community vigorously moves towards new experimental infrastructures to resolve outstanding key questions in neutrino astro- and particle physics, notably the neutrino mass hierarchy, the octant of Θ23, leptonic CP-violation, neutrino-less double beta decay and sterile neutrinos. Large new underground detectors and neutrino-telescope extensions would not only allow to study those intrinsic neutrino particle properties, but also to observe neutrinos from galactic super novae, from the sun and the Earth.  Continua a leggere Neutrinos in Astro- and Particle Physics


Looking for ‘new physics’ in the Universe

Con il termine “nuova fisica” si intende un nuovo campo di ricerca che tenta di spiegare quei fenomeni della natura che i fisici non sono ancora in grado di descrivere. Oggi, sta prendendo piede sempre più l’idea in base alla quale l’Universo può essere caratterizzato da una struttura diversa rispetto a quanto previsto dagli attuali modelli o teorie. In tal senso, un gruppo di fisici hanno avviato uno studio che avrà lo scopo di aiutare gli scienziati a rendere più facile, almeno in parte, la comprensione di alcuni fenomeni della fisica fondamentale.

New physics is about searching for unknown physical phenomena not known from the current perception of the Universe. Such phenomena are inherently very difficult to detect“, explains Matin Mojaza from CP3-Origins. Together with colleagues Stanley J. Brodsky from Stanford University in the U.S. and Xing-Gang Wu from Chongqing University in China, Mojaza has now succeeding in creating a new method that can make it easier to search for new physics in the Universe (post).

The method is a so called scalesetting procedure, and it fills out some empty, but very important, holes in the theories, models and simulations, which form the basis for all particle physics today.

With this method we can eliminate much of the uncertainty in theories and models of today“, says Matin Mojaza. Many theories and models in particle physics today has the problem that they, together with their predictions, provide some parameters that scientists do not know how to set. “Physicists do not know what values they should give these parameters. For example, when we study the Standard Model and see these unknown parameters, we cannot know whether they should be interpreted as conditions that support or oppose to the Standard Model, this makes it quite difficult to study the Standard Model accurately enough to investigate its value”, explains Matin Mojaza. With the new approach researchers can now completely clean their models for the unknown parameters and thus become better at assessing whether a theory or a model holds water.

The Standard Model has for the last 50 years been the prevailing theory of how the Universe is constructed. According to this theory, 16 (17 if we include the Higgs particle) subatomic particles form the basis for everything in the Universe.

But the Standard Model is starting to fall short, so it is now necessary to look for new physics in the Universe. One of the Standard Model’s major problems is that it cannot explain gravity, and another is that it cannot explain the existence of dark matter, believed to make up 25 percent of all matter in the Universe. In addition, the properties of the newly discovered Higgs particle, as described in the Standard Model, is incompatible with a stable Universe. “A part of the Standard Model is the theory of quantum chromodynamics, and this is one of the first things, we want to review with our new method, so that we can clean it from the uncertainties“, explains Matin Mojaza. The theory of quantum chromodynamics predicts how quarks (such as protons and neutrons) and gluons (particles that keeps quarks in place inside the protons and neutrons) interact. Matin and his Chinese and American colleagues now estimate that there may be a basis for reviewing many scientific calculations to clean the results from uncertainties and thus obtain a more reliable picture of whether the results support or contradict current models and theories. “Maybe we find new indications of new physics, which we would not have exposed if we had not had this new method”, says Matin Mojaza.

He believes that the Standard Model needs to be extended so that it can explain the Higgs particle, dark matter and gravity.

One possibility in this regard is to examine the so-called technicolor theory, and another is the theory of supersymmetry. According to the supersymmetry theory, each particle has a partner somewhere in the Universe (these have not yet been found though). According to the technicolor theory there is a special techni-force that binds so-called techni-quarks, which can form other particles, perhaps this is how the Higgs particle is formed. This could explain the problems with the current model of the Higgs particle. Also Rolf-Dieter Heuer, director of CERN in Switzerland, where the famous 27 km long particle accelerator, the LHC, is situated, believes that the search for new physics is important. According to him, the Standard Model cannot be the ultimate theory, and it is only capable of describing about 35 percent of the Universe. Like CP3-Origins, also CERN has put focus on weeding out old theories and search for new physics, this happening in 2015, when the accelerator starts up again (post).

University of Southern Denmark: New groundbreaking research may expose new aspects of the Universe

arXiv: A Systematic All-Orders Method to Eliminate Renormalization-Scale and Scheme Ambiguities in PQCD

Windows on the Universe

The Inaugural Conference of the ICISE on Windows on the Universe will review the most recent status of Particle Physics, Astroparticle and Cosmology. The conference will consist of plenary sessions for invited indepth oral presentations (review talks and talks on specific specialised topics), and contributed papers, in the form of relatively short oral papers – in parallel sessions – or posters. Special emphasis is being placed on active participation by young researchers and post-docs.

The main topics of the conference are:

  • Particle Physics
    • Production and Properties of the Higgs Boson
    • Searches for New Physics
    • Phenomenology of Physics Beyond the Standard Model
    • Production and Properties of the Heavy Quarks
    • Studies of Electroweak and QCD physics
    • Latest Results from Heavy Ion Collisions
    • Recent Results from the Intensity Frontier
    • Neutrino Physics from the Laboratory
    • Future Facilities (Accelerators)
  • AstroParticle Physics and Cosmology
    • Gamma-Ray Astronomy : Ground-Based and Satellite Experiments
    • Cosmic Rays : Ground-Based and Satellite Experiments
    • Multi Messenger Astronomy (Neutrinos, CR and GW)
    • Dark Energy and Dark Matter
    • The Cosmic Background Radiation
    • The Early Universe
    • Large Scale Structures
    • Future Facilities (Satellites and Telescopes)

No sign of supersymmetry yet from LHC data

I rivelatori LHCb e CMS situati presso l’acceleratore LHC del CERN di Ginevra hanno permesso di realizzare la prima e definitiva osservazione di una particella, denominata mesone Bs, che decade in due muoni. Questi risultati presentano delle implicazioni importanti per la ricerca di nuove particelle ed interazioni fondamentali, anche se si tratta di un altro colpo per coloro che sperano di rivelare le prime tracce della supersimmetria. Nonostante la fisica attuale spieghi solo il 5% del contenuto materia-energia dell’Universo, le cosiddette particelle supersimmetriche rappresentano una delle tante categorie di particelle candidate a spiegare la materia scura, che costituisce quasi il 27% del contenuto materia-energia dell’Universo.

According to professor Tara Shears, from the University of Liverpool’s Department of Physics, this observation is one of the rarest processes in fundamental physics and represents a fantastic confirmation of the Standard Model of particle physics. She explains: “It is one of the most frustrating confirmations we’ve ever had. We know our theory is incomplete, and this ultra-rare decay may give us clues as to what might replace it. But what this discovery tells us is that there are no signs yet of our best alternative, a theory called supersymmetry (SUSY)“.

We haven’t ruled out SUSY entirely, but we’ve definitely dismissed many of the most popular versions of it. We know that there must be new physics, but it’s starting to look like this might be stranger than we’d imagined. 

The decay observed at LHCb and CMS is predicted to be extremely rare in the Standard Model, with a Bs meson only decaying into two muons about 3 times in every billion. However, if ideas like SUSY are correct than the chances of the decay can be significantly increased or even suppressed. Hundreds of millions of collisions take place every second at the LHC, each one producing hundreds of new particles that leave electrical signals in the giant detectors. Physicists from LHCb and CMS trawled through two years’ worth of data, searching untold trillions of collisions for signs of two muons coming from a Bs meson. Professor Shears said: “It takes an enormous amount of data and hard work to sift out this tiny signal, and an incredibly precise particle detector to allow us to recognise the distinct experimental signature it leaves inside LHCb. Key to this is the VErtex LOcator (VELO), a precision silicon detector, at the core of LHCb, which physicists at the University of Liverpool designed and built. This detector is capable of resolving distances a fraction of a hair’s breadth in size, a precision which is needed to measure the distinctive flight distance inside LHCb that allows us to identify a Bs meson“. Neither LHCb nor CMS alone had enough data to announce a formal discovery, but when their results were formally combined the signal passed the all-important “five sigma” level, above which a discovery can be declared. This result is certainly not the end of the road for ideas like supersymmetry, which has many different versions, so many in fact that it is almost always possible to contort it so that it agrees with experimental data. However, combined with the recent discovery of the Higgs boson (post), whose mass is larger than predicted by many SUSY theories, this new result may force SUSY into such baroque configuration that the original motivation, a natural description of nature, is lost. Professor Shears added: “We’ve used all the data that LHC has delivered to us so far to make this measurement. What’s wonderful, and a very strong result, is that the CMS experiment has also performed the measurement on a completely separate dataset and seen the same thing. It’s a remarkable confirmation“.

University of Liverpool: CERN latest data shows no sign of supersymmetry – yet

The International Linear Collider: from design to reality

Il gruppo di ricercatori del Linear Collider Collaboration hanno pubblicato la relazione tecnica Technical Design Report (pdf) che riguarda la costruzione di un collisore lineare elettroni-positroni, lungo 31 chilometri, che permetterà di esplorare sempre di più il mondo delle particelle elementari in parallelo con il Large Hadron Collider.

In three consecutive ceremonies in Asia, Europe and the Americas, the authors officially handed the report over to the international oversight board for projects in particle physics, the International Committee for Future Accelerators (ICFA). The report presents the latest, most technologically advanced and most thoroughly scrutinized design for the ILC.

The ILC will accelerate and collide electrons and their antiparticles, positrons. Collisions will occur roughly 7000 times per second at the collision energy of 500 GeV.

Some 16,000 superconducting cavities will be needed to drive the ILC’s particle beams. The report also includes details of two state-of-the-art detectors that will record the collisions, as well as an extensive outline of the geological and civil engineering studies conducted for siting the ILC. “The Technical Design Report is an impressive piece of work that shows maturity, scrutiny and boldness“, says Lyn Evans, director of the Linear Collider Collaboration. “The International Linear Collider should be next on the agenda for global particle physics”. Among other particles, the ILC will produce Higgs bosons and study their properties in detail to determine whether they are as predicted by the Standard Model. Will the Higgs particle be just the first of a family? Will nature be more complicated than a single “minimal” Higgs boson? And how does the Higgs interact with other particles? Japan is considering offering to host the ILC for the global collaboration, siting it in the mountains of Japan. They propose to begin with a Higgs Factory and extend it to higher energies in the future. The ILC brings together more than 1000 scientists and engineers from more than 100 universities and laboratories in over two dozen countries.

LCC: International Linear Collider publishes its Technical Design Report

CERN: Next-generation particle accelerator is ready for construction – International Linear Collider publishes its Technical Design Report

Cosmology, Large Scale Structure and First Objects

Cosmology, Large Scale Structure and First Objects – This USP Conference shall cover the key issues of Cosmology, from particle physics, fundamental gravitation, cosmic background radiation, dark matter and dark energy, large-scale structure, simulations of the formation of structure in the Universe, as well as comparisons to observations.  Continua a leggere Cosmology, Large Scale Structure and First Objects