Tracking new physics—horse or zebra?

If you hear hoof beats, common sense says the cause is more than likely a horse. Yet, the possibility still exists that you’re actually hearing a zebra. Physicists at LHCb are applying that same logic to an unusual finding in…

If you hear hoof beats, common sense says the cause is more than likely a horse. Yet, the possibility still exists that you’re actually hearing a zebra. Physicists at LHCb are applying that same logic to an unusual finding in a recent analysis of the B meson.

Around one in every million B mesons decays into an excited kaon and two muons. The decay can occur in several different ways, so physicists classify them in what they call bins. The Standard Model predicts precisely the probability of the angles of these particle decays in each bin. The experiment can measure this probability, so it is an observable. Any difference between the measured observable and prediction could indicate new physics.
Nicola Serra of LHCb, one of the analysts of the B meson decay data from 2011, and his colleagues found such a difference.
“Most of the observables we measured in this analysis were close to Standard Model expectations, but a particular observable showed a sizable discrepancy,” he says.
On the ‘sigma’ scale that physicists use to describe the certainty of a result, Serra’s discrepancy between the expected and the measured result scored 3.7 sigma – there could be evidence for new physics but they need more data to confirm it. When they considered the probability of seeing that particular deviation with all of the data from the entire analysis, the sigma level dropped to 2.8 sigma, translating to a half a percent chance that the discrepancy is caused by statistical fluctuation. (The gold standard for a discovery is 5 sigma.)
A team of theorists then looked at the same decay and included more observables than the LHCb group did. They found, with this aggregation of many measurements, a consistent pattern of deviations that boosted the sigma to 4.5. That’s almost to the level of discovery, but within parameters that measure the presence of possible new physics. These parameters are more inclusive than those the LHCb team used.
“The theoretical interpretation is very interesting; that can’t be denied,” says Serra. “As an experimentalist, I have to focus on the data itself instead of the interpretation. If we see something that differs from the prediction, it’s crucial to understand if the pattern is real or not.”
If there’s a deviation from the prediction, experimentalists try to understand if something is wrong with the data. Only once all of the machine systematics and statistics are checked and double-checked can they say, with certainty, that there is a true discrepancy.
“The experimental paper only shows the data. The theory paper is the one that gives the interpretation. Both are pieces of a puzzle and they fit together nicely,” says Joaquim Matias, a theorist from Autonomous University of Barcelona and one of the paper’s authors. “The experimentalists found deviations and the theorists showed that they can be explained within a consistent picture for the first time.”
The data from this particular LHCb analysis show promise, encouraged by the theoretical possibilities, purported in the paper, of aggregated old and new LHCb data. But only once the full dataset undergoes the same treatment of crosschecks will the physicists determine if this decay is a horse or a zebra.
The LHCb team has started analysis of their total dataset, which is three times larger than the data presented in their paper. They expect to publish an update in the coming year. Both the experimentalists and theorists say that only a joint effort between their teams will allow them to establish whether this new physics anomaly is real.

Explore further:

First experimental signs of a New Physics beyond the Standard Model

Source:

CERN

view popular

4.5 /5 (15 votes)

Related Stories

First experimental signs of a New Physics beyond the Standard Model

Jul 31, 2013

The Standard Model, which has given the most complete explanation up to now of the universe, has gaps, and is unable to explain phenomena like dark matter or gravitational interaction between particles. Physicists …

Puzzling asymmetries in B decays hint at deviations from the Standard Model

May 28, 2012

(Phys.org) — In a recently published paper, the LHCb Collaboration has reported on a possible deviation from the Standard Model. Theorists are now working to calculate precisely this effect and to evaluate …

Discovery of rare decay narrows space for new physics

Jul 19, 2013

After a quarter of a century of searching, physicists have discovered a rare particle decay that gives them an indirect way to test models of new physics.

CERN latest data shows no sign of supersymmetry – yet

Jul 25, 2013

Physicists at Liverpool played a significant role in the development of the VErtex LOcator (VELO), a precision silicon detector, at the core of LHCb. The VELO detector consists of 42 separate modules (shown here), which were …

Confining supersymmetry: LHCb presents evidence of rare B decay

Nov 13, 2012

Today, at the Hadron Collider Physics Symposium in Kyoto, the LHCb collaboration has presented the evidence of a very rare B decay, the rarest ever seen. The result further shrinks the region in which scientists …

CERN experiments put Standard Model to stringent test

Jul 19, 2013

New results to be presented at the EPS-HEP conference in Stockholm, Sweden, this afternoon have put the Standard Model of particle physics to one of its most stringent tests to date. The CMS and LHCb experiments at CERN’s …

Recommended for you

Better insight into molecular interactions

1 hour ago

How molecules in biochemical solutions do interact, is a question of great importance for understanding processes in catalysts, functional materials and even in organisms. Until now, scientists could have …

Planes, trains and molecules: Deriving a generic routing algorithm from the physics of interacting polymers

20 hours ago

Finding a single optimal route is easy, but optimizing the combination of multiple routes is a challenge found in a wide range of applications including Internet instant messaging, peer-to-peer networks, subway …

New findings on how the ear hears could lead to better hearing aids

23 hours ago

A healthy ear is much better at detecting and transmitting sound than even the most advanced hearing aid. But now researchers reporting in the August 20 issue of the Biophysical Journal, a Cell Press public …

Mobius strip ties liquid crystal in knots to produce tomorrow’s materials and photonic devices

Aug 20, 2013

University of Warwick scientists have shown how to tie knots in liquid crystals using a miniature Möbius strip made from silica particles.

Researchers develop model to help control cascading events

Aug 19, 2013

(Phys.org) —A team of researchers at the University of California has developed a model that might lead to a better way to control natural cascading events such as landslides, earthquakes, or even neural …

Bright light, big mirror: Precision X-ray focusing at NSLS-II

Aug 16, 2013

(Phys.org) —Why does a packet of electrons whizzing around a half-mile ring at nearly the speed of light need a state-of-the-art mirror? It’s not to check its hair, that’s for sure.

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

More news stories

Planes, trains and molecules: Deriving a generic routing algorithm from the physics of interacting polymers

Finding a single optimal route is easy, but optimizing the combination of multiple routes is a challenge found in a wide range of applications including Internet instant messaging, peer-to-peer networks, subway …

Better insight into molecular interactions

How molecules in biochemical solutions do interact, is a question of great importance for understanding processes in catalysts, functional materials and even in organisms. Until now, scientists could have …

Teleportation just got easier—but not for you, unfortunately

Thanks to two studies published in Nature last Thursday, the chance of successful teleportation has considerably increased. Which is a good thing, right? …

The brilliance of diamonds

For the U.S. Department of Energy’s Argonne National Laboratory, diamond technology has been a gem of an idea.

Researchers discover quantum algorithm that could improve stealth fighter design

(Phys.org) —Researchers at the Johns Hopkins University Applied Physics Laboratory (APL) have devised a quantum algorithm for solving big linear systems of equations. Furthermore, they say the algorithm could be used to …

Viewing Fukushima in the cold light of Chernobyl

The Fukushima Daiichi nuclear disaster spread significant radioactive contamination over more than 3500 square miles of the Japanese mainland in the spring of 2011. Now several recently published studies …

Implications, solutions for US health disparities discussed

(HealthDay)—Research on health disparities in the United States, the policy implications of these disparities, and suggestions for improvement of disparities are discussed in “Health Policy Brief: Health …

Use of tPA for ischemic stroke nearly doubled from 2003 to 2011

Use of the “clot-busting” drug tissue plasminogen activator (tPA) to treat patients with strokes caused by a blockage of blood flow nearly doubled between 2003 and 2011. In their paper receiving online release in the journal …

Psychotherapy lags as evidence goes unheeded

Psychotherapy has issues. Evidence shows that some psychosocial treatments work well for common mental health problems such as anxiety and depression and that consumers often prefer them to medication. Yet …

Study examines overlooked role fruit-eating crocodilians may play in forest regeneration

It turns out that alligators do not live on meat alone. Neither do Nile crocodiles. A new study led by the Wildlife Conservation Society says that the American alligator and a dozen other crocodile species …