‘God Particle’ Rumor Dispelled: No Higgs Detected at LHC, CERN, Says ATLAS Report

The confirmation of the negative is finally here. A report has been released from ATLAS, CERN, which, after extensive analysis, has put to rest all rumors about any detection of the Higgs Boson the God Particle, which is supposed to endow all particles in the Universe with mass. We covered the news of the rumor here, urging readers to take the rumor with a healthy pinch of salt. The aforementioned report, surely enough and as we predicted, hasn’t found any Higgs.

The ATLAS Detector

The bottom line: The Higgs remains as elusive as ever, and physicists remain hopeful.

The news of this negative report was greeted with a little disappointment and lot of relief from the physics community, the latter emotion stemming from the fact that the Higgs was never expected at the position it was reported to have been found by the leaked memo. Many physicists were also appalled by the way a confidential memo was leaked a violation of both the ethical code of conduct and a personal breach of innate scientific spirit.

The present report (about the di-photon mass spectrum) from ATLAS has a lot more data points than the memo, and the data has been thoroughly analyzed. Find the report here. The key diagram in the report is given below.

Forget all the complications and the different plots. Note the monotonic step-like appearance of the plot. If the Higgs were detected, you’d find bumps in the graph (or at least one bump) localized at particular energies. If the memo were really right about the detection, there would have been a bump at 115 GeV (on the yellow band above the number 115′ marked on the horizontal axis), as the memo had reported the detection at this temperature. No irregularity is found, as is plainly visible to the naked eye.

There’s no real ambiguity anymore. At the risk of sounding repetitive, let’s say it once more: The Higgs has not been found.

If the Standard Model is correct, however, you should expect news of detection soon enough, especially when higher energy ranges are being probed. Watch this space…

Eureka Moment: New Particle Discovered At Tevatron?

This is big, really big! This may be the biggest news to hit the particle physics world in the the last 50 years. Scientists, analyzing the data collected at the Tevatron, Fermilab, have detected an anomaly that could well usher in a new dawn in theoretical physics and change the Standard Model as we know it now. The observation was a bump in the data, but in the ‘wrong’ place.

Tevatron
Tevatron

Scientists are excited about a Gaussian peak that has been observed on Wednesday, 6th April, centered at about 150 GeV with a spread of 2.5 GeV, corresponding to nearly 300 events.

Data Analysis:

Physicists are generally quite skeptical about any news of big breakthroughs. This ensures that the discoveries are really authentic. Most ‘discoveries’ are just mistakes in the code being used for data-analysis, or some human error or plain background fluctuations. All of these have to be ruled out. Coding errors can be ruled out by using many orthogonal samples of data, called ‘control sets’. Background fluctuations take a bit more effort, but routine analysis can eliminate it almost completely. A peak left after background elimination cannot be discarded.

Notwithstanding the fact that physicists are extremely skeptical, almost all major discoveries in high energy physics have been accidental. The key to such a discovery is rigorous analysis of data.

Is this the Higgs Boson?

The knee-jerk reaction was to suspect the discovery of the Higgs, the bosonic particle that is believed to endow all fundamental particles with mass. The Higgs boson, however, is ruled out, because if the Higgs could be produced at 140 GeV at a non-negligible rate, then we expect to see the characteristic decay jets, which would consist, mainly, of bottom quarks. However, such jets have not been observed, ruling out this possibility.

Higgs Event at CMS
Higgs Event at CMS, LHC

Is this a new force of nature?

It is too early to comment. The discovery of a new particle – a new boson – has to be confirmed. Only further investigation can answer this question.

What could fit the fill?

A new particle, which was coincidentally proposed in a paper a few days back, could fit the bill. The particle is called the Z’ boson, as compared to the Z boson. The Z’ boson is expected to decay via semi-leptonic (i.e. a mixture of hadrons and leptons) channels. Semi-leptonic jets have been observed. So, maybe, the Z’ is the ‘new’ particle.

Decay event for the Higgs
Higgs Decay

Confidence Levels:

The result now stands with a 3-sigma confidence level. This means that the possibility of ruling out the observation as a statistical fluctuation is less than 1 percent. Physicists look for a 6-sigma confidence level, which means that the doubts should reduce to less than 0.003%. To attain this level of confidence, scientists will need more sets of data and rigorous analysis of the same.

More data is on the way. As Prof. Nima Arkani-Hamed of the Institute for Advanced Studies, Princeton, notes, LHC should come up with much more data and copious events, if this is indeed a real discovery.

An Event at the Large Hadron Collider
A Collision Event at the Large Hadron Collider

One thing is for sure: this is exciting. If this is true, this is pure gold for particle physicists.

UPDATE: Fermilab rejects new particle discovery after extensive data analysis. Read here.