Wednesday, November 30, 2011

The not-so-Elusive Neutrinos

What we know about neutrinos, what do we want to find out, and why do we care?
Super-K data. Image from the t2k site.
Neutrinos are the smallest, neutral particles scientists have observed other than photons. Their name is well chosen. Neutrino means the small, neutral one in Italian. They come in three flavors: the electron, muon and tau neutrino. We know mass differences between flavors and that neutrinos can oscillate between the three available flavors as they travel through space. The probability of measuring a particular flavor for a neutrino varies periodically as the particle propagates.

What we do not know is the actual masses of the neutrinos or if the neutrinos can be their own anti-particle. Some experiments such as the T2K will measure neutrino oscillations more accurately and others such as the Majorana experiment constrain the neutrino mass. The cool thing about neutrinos is that they interact very weakly with other particles and fields.  This is why they come out early from very dense and hot places.  They can carry information from supernovae remnants, the core of the sun or the Galactic center. They provide unique information about objects produced in messy environments such as young neutron stars that we could not study otherwise.

Why have I written this post?
I have attended two seminars on neutrino experiments. We had a speaker from the T2K (Tokai to Kamioka) collaboration and one from the Majorana demonstrator. The message of the talks was largely that while there has been significant progress made, we have the technology to build better experiments and we are building them. Both talks were good, but I wish they had spent a few slides talking about the broader impacts of their research vs. just the details of their results. However, these talks stimulated me to brush up my knowledge of neutrinos and write this post.

Monday, November 28, 2011

The Large Hadron Collider and the Origin of Mass

Beam tubes at the LHC. Credit: CERN.
This grandiose title is for an inaugural lecture across town that is targeted at a general audience.  The speaker is a young professor at ITP, Stefano Pozzorini. Once a person receives a professorship at the University of Zurich, which does not have to be a permanent position, they have to sustain this type of public lecture. It's dark out already. The talk starts at 6:15 p.m. and is followed by a small reception. I hope I will find the building and the room.

Update: I did find the building. It is one of the most beautiful buildings on campus with columns, writing in latin and majestic horse statues at the entrance. The auditorium was equally impressive. The ceiling is tens of meters high and the walls are covered with imitations of sculptures from thousands of years ago.

The seminar was interesting. It often happens that general audience seminars end up at a low enough level so that I understand some part of what they say, but not low enough for the targeted audience. The talk was about detecting the Higgs boson. The Higgs boson is a spin zero, scalar particle that is necessary to explain how most elementary particles obtain their mass in the Standard Model. It would give mass to every elementary particle that couples with it including the Higgs itself. The data from Large Hadron Collider (LHC) has excluded heavy and mid-mass Higgs bosons. The hope is that the Higgs is light (around 120 GeV) and will be discovered soon.

The profile of one of the first beams to collide in the LHC. Credit: CERN.
 The LHC is a detector that collides high energy protons or lead nuclei. The term hardon means it collides particles made of quarks. The protons and neutrons are heavy and made out of quarks, while the electron is still believed to be an elementary particle. It shuts down for the winter and will be operating for another 8 months starting in February. Afterwards, it shuts down for 2 years for upgrades. The proton beams have only reached half their design energy and are expected to reach the full 7 TeV per beam after this upgrade. The University of Zurich designed/built the inner track system of one of the detectors within the LHC, which determines the resolution with which the charged particles are detected.

The expectation was that they would find a new family of particles with the Higgs as a certain detection. So far they have not detected any new particles. If they do not find the Higgs, then the Standard Model is incorrect. One of the most minor modifications of the Standard Model is that there is a "invisible" sector of Higgs particles. This would mean that there are fewer "visible" Higgs particles than previously thought and hence harder to detect. The consensus from this talk was that we will find out very soon if there is a Higgs boson in the mass range they search and that we should just wait for data vs. speculate wildly. Speculation is fun, though...

I arrived home at almost 9 p.m. after I missed one of the buses. These long days at work do have a price and sometimes I wonder if this price is worth paying. I guess there must be some balance between activities and, in general, some balance in life that I still have to find.

The First Post

Me in 2008.
I first started this blog to replace the sporadic writing I do at the the end of my research notebooks or in random text files. Not all my thoughts are or should be made public, but I do feel a need to both write more about what I do and share some of it with the world.
 I am not committing to writing every day or even every week.  Sometimes I may give too much information and sometimes too little. I apologize for that in advance. I do not have a target audience in mind. The purpose of this blog is to document some of my own personal growth over a period of a few years, and to practice writing. As long as I find it meaningful and fun, I will continue posting.

This blog voices my personal opinions of random topics, events, seminars and personal experiences.  It is not approved by or representative of any institution, collaboration or anybody else other than me. While some of the information is scientific or quasi-scientific, keep in mind that this is a personal blog and it describes my understanding of the various phenomena and topics I write about. What I write can be wrong. I do hope I am not wrong too often, though.

So, does what I write have value? It's hard to say.  It certainly has value to me. I enjoy writing about the people I love, and about the various positive experiences in my life. It sometimes helps me cope with the stress that often comes in large quantities. Also, the more I work and the more applications I submit, the more I feel the need to prove to myself and to the world that I am a whole person with hopes, and dreams and troubles, and somehow writing helps towards that.

I hope that my children, nephews and nieces will enjoy reading some of these posts when they are grown and not feel too embarrassed by them. For them, I have also started combing my description of the present with some from the past.  If somehow I fail to tell them the stories myself, I want them written down.