Τα ελληνικά ΜΜΕ για τον LHC

[apolski]

Το οτι τα φωτονια ειναι αμαζα ειναι μια υποθεση, πειραματικα απλως εχει βρεθει ενα ανω οριο στην μαζα τους. Οποτε το αποτελεσμα του Opera, αν ειναι σωστο, ισως ειναι μια ενδειξη για το οτι τα φωτονια εχουν μαζα

[papagalakos]

[youtube]http://www.youtube.com/watch?v=zdI7LQm9cJE[/youtube]

[apolski]

Potential mistakes in the Opera research
http://motls.blogspot.com/2011/09/poten ... earch.html

Superluminal neutrinos from noncommutative geometry
http://motls.blogspot.com/2011/09/super ... -from.html

[apolski]

Η αμφισβήτηση των υπερφωτεινών νετρίνων του πειράματος OPERA

1) Οι Andrew Cohen και Sheldon Glashow στο άρθρο τους New Constraints on Neutrino Velocities αναφέρουν:
«Σύμφωνα με την ανακοίνωση της ομάδας του πειράματος OPERA, νετρίνα του μιονίου, με μέση ενέργεια 17.5 GeV, διέσχισαν την απόσταση των 730 km από το CERN στο Gran Sasso, και βρέθηκε ότι κινήθηκαν με ταχύτητα μεγαλύτερη της ταχύτητας του φωτός κατά 7,5 km/s.

Όμως αποδεικνύεται ότι, αν υποθέσουμε την ύπαρξη τέτοιων υπερφωτεινών νετρίνων, τότε αυτά θα χάνουν την ενέργειά τους γρήγορα, εξαιτίας της δημιουργίας των ζευγών ηλεκτρονίου-ποζιτρονίου:


Οι υπολογισμοί δείχνουν ότι τα περισσότερα νετρίνα θα έπρεπε να υποστούν αρκετές εκπομπές ζευγών στη διαδρομή, με αποτέλεσμα η δέσμη να απογυμνώνεται από τα υψηλής ενέργειας νετρίνα. Και ως εκ τούτου αμφισβητoύμε το αποτέλεσμα του OPERA.»





2) O Carlo Contaldi, στο άρθρο του The OPERA neutrino velocity result and the synchronisation of clocks ισχυρίζεται ότι οι μετρήσεις ταχύτητας σαν αυτή που πραγματοποίησε το πείραμα OPERA απαιτούν κατάλληλο συγχρονισμό ρολογιών σε μη αδρανειακά συστήματα δεδομένου ότι η Γη περιστρέφεται.

Σύμφωνα με τον Carlo Contaldi, τo πείραμα OPERA δεν έλαβε υπόψη το γεγονός ότι ένταση του πεδίου βαρύτητας στο CERN δεν είναι ίδια με την ένταση στο Gran Sasso. Σύμφωνα με τη Γενική Θεωρία της Σχετικότητας μικρές διαφορές στη βαρύτητα σε δυο τόπους κάνει τα ρολόγια δουλεύουν με διαφορετικούς ρυθμούς.

Ο Dario Autiero από το Ινστιτούτο Πυρηνικής Φυσικής στη Λυών (IPNL), και συντονιστής του πειράματος, απαντά ότι τα ρολόγια ήταν σωστά συγχρονισμένα και ότι θα υποβάλλει προς δημοσίευση περισσότερες λεπτομέρειες, έτσι ώστε να ξεκαθαρίσουν τα πράγματα.

http://physicsgg.blogspot.com/2011/10/opera.html

[snodrion]

http://tvxs.gr/news/sci-tech/nees-metri ... etikotitas

[Ιάσωνας]

This year's hunt for the Higgs boson is drawing to a close. On 30 October, the Large Hadron Collider (LHC) at CERN, Europe's particle-physics laboratory near Geneva, will end its 2011 run of the proton–proton collisions that search for the elusive particle, thought to give other fundamental particles their mass.

But physicists believe that the collider will have collected enough data by the end of 2012, after experiments resume in March, to say whether the Higgs exists. In fact, they say, strong hints of whether or not it exists may be present in data already collected. "We are entering the golden year for the Higgs search," says Guido Tonelli, spokesman for the LHC's CMS experiment, one of the detectors that is used in the search for the Higgs boson, "and in the next few months we may be able to give important messages."
Higgs hints

There have been tantalizing hints already. In July, the ATLAS and CMS experiments at CERN reported a few "excess events" suggestive of the Higgs boson within the debris generated by the proton–proton collisions (see Hint of Higgs, but little more). But by August, with more data to analyse, the probability of these events being due to the Higgs, rather than simply statistical fluctuations in the data, had fallen from a significance of 2.8 sigma (corresponding to a more than 99% chance of being 'real') to 2 sigma (around 95% chance of being real), the opposite direction to what would be hoped (see Higgs signal sinks from view).

With double the amount of data now than they had in August, Tommaso Dorigo, a particle physicist at the University of Padua in Italy and a member of the CMS team, says he is "willing to bet a few bucks" that the small excess of events indicating that the Higgs boson has a mass of around 120 gigaelectronvolts, reported in July, really are due to the Higgs. And he estimates that, if is he right, then by the time the 2011 data are analysed early next year, the significance of the excess will have grown to about 3 sigma (a significance value of 5 sigma is the minimum at which discovery of the Higgs boson could definitely be claimed). "That would not be enough to claim a discovery," he says, "but it would be enough to convince most physicists that the effect is real."

Vivek Sharma of the University of California, San Diego, who heads the search for the Higgs at the CMS, points out that results from both CMS and ATLAS have already ruled out, with a confidence of 2 sigma, a Higgs mass of between about 145 and 400 gigaelectronvolts, and that the LHC's predecessor, the Large Electron Positron collider, ruled out a Higgs mass below about 114 gigaelectronvolts. So the Higgs, if it exists, almost certainly lies in the gap between the two. According to Sharma, the extra data to be collected in 2012 once proton-proton collisions resume in March will allow the CERN scientists to "either find the Higgs in this mass range, or wipe it out".
Sticking to the standard

Apart from the Higgs' no-show, results from the LHC so far have not pointed to any new physics beyond the 'standard model'. The decay patterns of particles known as Bs mesons, which consist of one 'bottom' and one 'strange' quark, remain in line with the predictions of the standard model and not with its extensions such as 'supersymmetry' — a class of theories which suggest that each known particle has an exotic and as yet unseen partner. In fact, physicists now believe that the simplest, and most popular, version of supersymmetry is probably not correct (see Beautiful theory collides with smashing particle data). "The data are less exciting than people had hoped," admits Adam Falkowski, a particle-physics theorist at the University of Paris-South in Orsay, France.

A positive result in the Higgs hunt would perhaps be a more obvious public-relations success for CERN, but for Falkowski a negative outcome would be more exciting, as it would, he says, "definitely mean new physics". He explains that it is not clear what that new physics might be, pointing out that a particle such as the Higgs may still exist but that other as-yet undiscovered particles cause it to decay in a unexpected way. Another, more radical possibility, he says, is that the breaking of the symmetry between the weak and the electromagnetic forces (for which the Higgs is believed to be responsible) could instead be carried out by a completely new set of very strong forces described by a theory called 'technicolour'.

"If the standard model is true then we wouldn't have much to do as theorists, but if the Higgs isn't found then a whole new world of possibilities opens up," Falkowski says.

Πηγή

[Ιάσωνας]

14-18 Νοεμβρίου, Φυσικοί, που ειδικεύονται στην Σωματιδιακή Φυσική, θα συναντηθούν στο Παρίσι, για να συζητήσουν τα αποτελέσματα από τη λειτουργία του LHC, το 2011.

http://hcp2011.lpnhe.in2p3.fr/

Επίσης:

[youtube]http://www.youtube.com/watch?v=ecaYiSyBvkM[/youtube]

[Ιάσωνας]

Φυσικοί, μηχανικοί και άλλοι επιστήμονες από όλο τον κόσμο συγκεντρώθηκαν στη Γενεύη, όπου και οι εγκαταστάσεις του CERN, θέτοντας τα θεμέλια για ένα μεγάλο πρόγραμμα που θα προσδώσει στο ισχυρότερο επιστημονικό μηχάνημα του πλανήτη μας ακόμα πιο εντυπωσιακές δυνατότητες σύγκρουσης σωματιδίων, σύμφωνα με το πρακτορείο Ρόιτερ.

Όπως δήλωσαν στελέχη του CERN, η φιλόδοξη προσπάθεια, στην οποία συμμετέχουν ερευνητικοί και ακαδημαϊκοί φορείς από την Ευρώπη, τις ΗΠΑ και την Ιαπωνία, θα απαιτήσει νέες τεχνολογικές καινοτομίες σε διάφορα πεδία, από τους υπεραγώγιμους μαγνήτες έως τις γραμμές μεταφοράς ενέργειας. Τελικός στόχος είναι ο επιταχυντής να είναι σε θέση να "ψάξει" ακόμα πιο βαθιά και εντατικά στα μυστήρια της ύλης και του σύμπαντος.

"Οι πρόσθετες δυνατότητες θα αυξήσουν κατά πολύ τις ικανότητές μας να κάνουμε μετρήσεις ακριβείας και να ανακαλύψουμε καινούρια πράγματα", δήλωσε ο διευθυντής ερευνών Σέρτζιο Μπερτολούτσι. Η πρωτοβουλία βρίσκεται ακόμα στο στάδιο του συντονισμού και της κατανομής εργασιών μεταξύ των συμμετεχόντων μερών.

Ο μεγάλος επιταχυντής βρίσκεται σε ένα κυκλικό υπόγειο τούνελ μήκους 27 χιλιομέτρων κάτω από τα γαλλο-ελβετικά σύνορα. Λειτουργεί από τον Μάρτιο του 2010 και ήδη έχει προσφέρει πλούτο επιστημονικών στοιχείων που βρίσκονται υπό ανάλυση.

Το μηχάνημα θα κλείσει φέτος τον Δεκέμβριο και για δύο μήνες περίπου, προκειμένου να γίνει η καθιερωμένη χειμερινή συντήρησή του. Στο τέλος του 2012, έχει προγραμματιστεί ο επιταχυντής να κλείσει για περίπου ένα έτος, ώστε να διπλασιάσει την ισχύ των συγκρούσεών του, με στόχο να προετοιμαστεί καλύτερα για την μελέτη φαινομένων όπως η σκοτεινή ύλη, η σκοτεινή ενέργεια και η υπερσυμμετρία.

Όμως θα είναι ο δεκαπλασιασμός των δυνατοτήτων του έως το 2020 που, όπως προσδοκάται από την επιστημονική κοινότητα, θα ανοίξει ένα μεγάλο "παράθυρο" σε ακόμα μεγαλύτερα μυστήρια της Φύσης, όπως η φύση του χρόνου και η πιθανή ύπαρξη παράλληλων συμπάντων.

Πηγή: News247.gr

[mplamplampla]

http://arxiv.org/pdf/1109.4897v2

[Hengeo]

Tα νετρίνα στο CERN επιμένουν να κινούνται ταχύτερα από το φως

[Ιάσωνας]

Πολύ κοντά στο αν υπάρχει ή όχι το μποζόνιο Higgs

CERN has been in effervescence for the last few weeks, with rumors running wild and hopes flying even higher. In fact, for the past few weeks, the physicists from ATLAS and CMS, the two collaborations looking for the Higgs boson at the Large Hadron Collider (LHC), have known half the answer. The problem is that the truth lies in knowing the other half, which will only be known officially at a special seminar organized by CERN director general on tomorrow December 13 at 14:00.

What can we expect to find out next Tuesday? Already, in November, the first combined results from the two experiments were released based on 40% of all collected data, excluding large values of the Higgs boson mass. This means, we now know better where to concentrate our efforts.

Looking for the Higgs has kept physicists on their toes for decades. In this case, the theory predicts the existence of this particle. Finding it would be one more confirmation, and a very strong one, that the theoretical description we currently have, the Standard Model, is correct.

At this point, the region at low mass, between 114 and 141 GeV, is where we expect to see something. The Standard Model predicts how many Higgs bosons should be produced at a given mass, and how many of them will decay in a specific way, but it does not tell us its mass. So CMS and ATLAS are searching blindly, not knowing exactly where to look, but also searching using all possible decay modes.

In the low mass range, three different decay channels contribute the most, namely when a Higgs boson decays into two photons, two Z bosons going into four leptons, or two W bosons decaying into two leptons and two neutrinos.

How and when will we know if we have indications from the Higgs boson? If one experiment sees hints of the Higgs boson not only from one channel, but two or even three of these channels, then it’s encouraging. Even better, if not one but both experiments see such signs, and both see them at the same mass, it’s time to call your mother.

This is very much like trying to catch a faint radio signal. We suspect this hidden radio station exists but nobody knows at which frequency it broadcasts. If one search team hears a weak signal using a crystal radio at a given frequency, this is one thing. But say another group also catches something independently at the same frequency using a digital radio, it gets more interesting.

For the Higgs boson, each decay channel represents one different type of detecting technology. Since CMS and ATLAS are looking without telling the other group what they have, if the results that will be presented tomorrow are similar, it could be an indication on the presence of the Higgs boson. But caution will be exerted until we have the irrefutable proof of its presence.

So, stay tuned on December 13 to find out what we have so far…. I will be tweeting live like a little bird from the seminar so you can follow the action as it unfolds from the @CERN account. My colleague Aidan Randle-Conde will be blogging live on the Quantum Diaries site. The seminar will also be broadcasted live from the CERN home page. I will also report the results here towards the end of the afternoon.

Pauline Gagnon

Πηγή

[Wizard]

Μέχρι τώρα αυτά που έχουν ειπωθεί από Atlas:
131-453 GeV έχουν αποκλειστεί με 95% βεβαιότητα.
Αρκετά καλή πιθανότητα το Higgs να είναι στα 126GeV. Νέα αποτελέσματα με τα δεδομένα του 2012

CMS:
Αποκλείει 127 έως 600 GeV, βλέπει 1.9σ πιθανότητα για κάτω από 130 GeV (το Atlas μιλάει για 2.3σ).

ATLAS and CMS experiments present Higgs search status

13 December 2011. In a seminar held at CERN today, the ATLAS and CMS experiments presented the status of their searches for the Standard Model Higgs boson. Their results are based on the analysis of considerably more data than those presented at the summer conferences, sufficient to make significant progress in the search for the Higgs boson, but not enough to make any conclusive statement on the existence or non-existence of the elusive Higgs. The main conclusion is that the Standard Model Higgs boson, if it exists, is most likely to have a mass constrained to the range 116-130 GeV by the ATLAS experiment, and 115-127 GeV by CMS. Tantalising hints have been seen by both experiments in this mass region, but these are not yet strong enough to claim a discovery.

Higgs bosons, if they exist, are very short lived and can decay in many different ways. Discovery relies on observing the particles they decay into rather than the Higgs itself. Both ATLAS and CMS have analysed several decay channels, and the experiments see small excesses in the low mass region that has not yet been excluded.



Taken individually, none of these excesses is any more statistically significant than rolling a die and coming up with two sixes in a row. What is interesting is that there are multiple independent measurements pointing to the region of 124 to 126 GeV. It’s far too early to say whether ATLAS and CMS have discovered the Higgs boson, but these updated results are generating a lot of interest in the particle physics community.



“We have restricted the most likely mass region for the Higgs boson to 116-130 GeV, and over the last few weeks we have started to see an intriguing excess of events in the mass range around 125 GeV,” explained ATLAS experiment spokesperson Fabiola Gianotti. “This excess may be due to a fluctuation, but it could also be something more interesting. We cannot conclude anything at this stage. We need more study and more data. Given the outstanding performance of the LHC this year, we will not need to wait long for enough data and can look forward to resolving this puzzle in 2012.”



“We cannot exclude the presence of the Standard Model Higgs between 115 and 127 GeV because of a modest excess of events in this mass region that appears, quite consistently, in five independent channels,” explained CMS experiment Spokesperson, Guido Tonelli. “The excess is most compatible with a Standard Model Higgs in the vicinity of 124 GeV and below but the statistical significance is not large enough to say anything conclusive. As of today what we see is consistent either with a background fluctuation or with the presence of the boson. Refined analyses and additional data delivered in 2012 by this magnificent machine will definitely give an answer.”



Over the coming months, both experiments will be further refining their analyses in time for the winter particle physics conferences in March. However, a definitive statement on the existence or non-existence of the Higgs will require more data, and is not likely until later in 2012.



The Standard Model is the theory that physicists use to describe the behaviour of fundamental particles and the forces that act between them. It describes the ordinary matter from which we, and everything visible in the Universe, are made extremely well. Nevertheless, the Standard Model does not describe the 96% of the Universe that is invisible. One of the main goals of the LHC research programme is to go beyond the Standard Model, and the Higgs boson could be the key.



A Standard Model Higgs boson would confirm a theory first put forward in the 1960s, but there are other possible forms the Higgs boson could take, linked to theories that go beyond the Standard Model. A Standard Model Higgs could still point the way to new physics, through subtleties in its behaviour that would only emerge after studying a large number of Higgs particle decays. A non-Standard Model Higgs, currently beyond the reach of the LHC experiments with data so far recorded, would immediately open the door to new physics, whereas the absence of a Standard Model Higgs would point strongly to new physics at the LHC’s full design energy, set to be achieved after 2014. Whether ATLAS and CMS show over the coming months that the Standard Model Higgs boson exists or not, the LHC programme is opening the way to new physics.

[Ιάσωνας]

Νέο υποατομικό σωματίδιο στο CERN

The Large Hadron Collider (LHC) on the Franco-Swiss border has made its first clear observation of a new particle since opening in 2009.

It is called Chi_b (3P) and will help scientists understand better the forces that hold matter together.

The as-yet unpublished discovery is reported on the Arxiv pre-print server.

The LHC is exploring some of the fundamental questions in "big physics" by colliding proton particles together in a huge underground facility.

Detail in the sub-atomic wreckage from these impacts is expected to yield new information about the way the Universe is constructed.

The Chi_b (3P) is a more excited state of Chi particles already seen in previous collision experiments, explained Prof Roger Jones, who works on the Atlas detector at the LHC.

"The new particle is made up of a 'beauty quark' and a 'beauty anti-quark', which are then bound together," he told BBC News.

"People have thought this more excited state should exist for years but nobody has managed to see it until now.

"It's also interesting for what it tells us about the forces that hold the quark and the anti-quark together - the strong nuclear force. And that's the same force that holds, for instance, the atomic nucleus together with its protons and the neutrons."

The LHC is designed to fill in gaps in the Standard Model - the current framework devised to explain the interactions of sub-atomic particles - and also to look for any new physics beyond it.

In particular, it is using the collisions to try to pin down the famous Higgs particle, which physicists hypothesize can explain why matter has mass.

Discoveries such as Chi_b (3P) are an important part of this quest because they add to the wider background knowledge, says Prof Jones, from Lancaster University, UK.

"The better we understand the strong force, the more we understand a large part of the data that we see, which is quite often the background to the more exciting things we are looking for, like the Higgs.

"So, it's helping put together that basic understanding that we have and need to do the new physics."

Prof Paul Newman, from the University of Birmingham, added: "This is the first time such a new particle has been found at the LHC. Its discovery is a testament to the very successful running of the collider in 2011 and to the superb understanding of our detector which has been achieved by the Atlas collaboration already."

And Andy Chisholm, a PhD student from Birmingham who worked on the analysis, said: "Analysing the billions of particle collisions at the LHC is fascinating. There are potentially all kinds of interesting things buried in the data, and we were lucky to look in the right place at the right time."

Πηγή: BBC

[apolski]

BREAKING NEWS: Error Undoes Faster-Than-Light Neutrino Results

It appears that the faster-than-light neutrino results, announced last September by the OPERA collaboration in Italy, was due to a mistake after all. A bad connection between a GPS unit and a computer may be to blame.

Physicists had detected neutrinos travelling from the CERN laboratory in Geneva to the Gran Sasso laboratory near L'Aquila that appeared to make the trip in about 60 nanoseconds less than light speed. Many other physicists suspected that the result was due to some kind of error, given that it seems at odds with Einstein's special theory of relativity, which says nothing can travel faster than the speed of light. That theory has been vindicated by many experiments over the decades.

According to sources familiar with the experiment, the 60 nanoseconds discrepancy appears to come from a bad connection between a fiber optic cable that connects to the GPS receiver used to correct the timing of the neutrinos' flight and an electronic card in a computer. After tightening the connection and then measuring the time it takes data to travel the length of the fiber, researchers found that the data arrive 60 nanoseconds earlier than assumed. Since this time is subtracted from the overall time of flight, it appears to explain the early arrival of the neutrinos. New data, however, will be needed to confirm this hypothesis.

http://news.sciencemag.org/scienceinsid ... aster.html

[kostas213]

Οπότε λύθηκε το μυστήριο πρακτικά. Ήταν όντως πολύ κουλό για να είναι αληθινό!