Posted by Bilal Aslam
By: Dr. Mansoora Shamim (for her VITA see below)
University of Oregon
July 17, 2012
Knowing the secrets about beginning and evolution of universe and understanding the basic constituents of matter and interactions between them has always been the utmost desire of human beings.
The Large Hadron Collider (LHC) with its twenty-seven kilometer long tunnel around the outskirts of Geneva was built to provide answers to many questions like: What is the origin of mass? How the universe came into existence? What were the exact conditions that created different kinds of particles? What are the missing components in understanding the universe? Why is there only matter and no antimatter seen in our universe?
Just three years after the ending of World War II, a Nobel Prize winning physicist Louis de Broglie proposed the plan of a European physics laboratory. Initially twelve countries signed the treaty and the Conseil Europée pour la Recherche Nucléaire (European Nuclear Research Council) or CERN was formed. In 1952, Geneva, Switzerland was chosen as the site for the laboratory. The LHC was approved in 1995 with a budget of 2.6 billion Swiss Francs. The actual cost by the time of completion ran over by 480 million Swiss Francs.
LHC is the world`s largest collider which collides particles at the highest possible energies available. It resides in a tunnel that passes under the French and Swiss countryside 100 m underground. It accelerates two beams of protons to the speed very close to the speed of light. The two oppositely moving beams are squeezed down to the fraction of the width of a human hair and brought closer to collide with each other at four different points around the LHC ring where the detectors ATLAS, CMS, ALICE and LHCb are located. The energy and the temperature available at LHC at the time of collisions are similar to that existed a few moments after the big bang. According to the theory of Big Bang, the universe was initiated from a singularity, which suddenly erupted releasing the trapped mass leading yet again into the creation of a new universe through the event horizon. When the colliding particles in the LHC break, new particles are produced. The new particles are detected using very previse and sophisticated instruments called detectors which serve as high-resolution cameras. By analyzing the data that contains new particles, one can determine the properties of particles and the existing forces among them. It can also be estimated what kind of circumstances were at the time of big bang. The LHC has been fully operational since March 2010.
The basic atomic model states that in an atom, protons and neutrons make up the nucleus and electrons revolve around the nucleus. Electrons are elementary particles, which means they do not have any sub structure while this is not true for protons and neutrons. They are composed of more fundamental particles called quarks. All elementary particles which make up the matter of the universe, are divided into two groups: quarks and leptons. Examples of leptons include electron, muon, tau and neutrinos while those for quarks include up, down, charm, strange, top and bottom quark. The four types of forces through which particles interact with each other are strong, electromagnetic, weak and gravitational interactions. The strong force that exists at the sub-nuclear level holds quarks together within proton. The electromagnetic force is responsible for chemical reactions as well as electrical and magnetic phenomena. The weak force manifests itself in radioactivity and β-decays- the processes that makes sun shine while the gravitational interaction is responsible for gravity. Gravitational force is only important at the large scale and can be ignored when we talk about the objects whose sizes are of the order of 1 fm (10−15 m) which is the size of a proton. In the Glashow–Weinberg–Salam (GWS) theory, also known as the standard model, electroweak interactions arise from the exchange of photons and of massive charged W and neutral Z bosons between quarks and leptons. In 1979, the Nobel Prize in Physics was awarded jointly to Sheldon Lee Glashow, Abdus Salam and Steven Weinberg “for their contributions to the theory of the unified weak and electromagnetic interaction between elementary particles, including, inter alia, the prediction of the weak neutral current”. Furthermore, in 1984 the Nobel Prize in Physics was awarded jointly to Carlo Rubbia and Simon van der Meer “for their decisive contributions to the large project, which led to the discovery of the field particles W and Z, communicators of weak interaction”.
The standard model of particle physics does not explain the fact how different particles acquire mass and why some particles are heavy while others are light. What it predicts is the existence of a new object/field. It is assumed that the whole space is filled with this field and particles acquire mass by interacting with this field. In 1960s Peter Higgs proposed spontaneously broken symmetry in electroweak theory explaining the origin of mass of elementary particles in general and of the W and Z bosons in particular. This so-called Higgs Mechanism, which was proposed by several physicists besides Higgs at about the same time, predicts the existence of a new particle “Higgs boson”. If such a particle exists the experiments at the LHC should be able to detect it.
On July 4, 2012 at a seminar held at CERN, ATLAS and CMS experiments announced the observation of a particle consistent with long-sought Higgs boson in the mass region around 125-126 GeV. This is a milestone as well as a breakthrough in the field of particle physics and understanding of universe. Both experiments have observed clear signs of a new particle in the mass region around 126 GeV. The probability that this particle does not exist is negligible (about one in three million). The implications are very significant and it is precisely for this reason that extremely diligent crosschecks are required in future studies. The observation of this new particle indicates the path for the future towards a more detailed understanding of what we are seeing in the data. The results presented are based on data collected in 2011 and 2012 at center of mass energy of 7 and 8 TeV (To remind the reader that 1TeV is equivalent to the energy of a flying mosquito.) respectively. A more complete picture of these observations will emerge later this year after the LHC provides the experiments with more data.
The next step will be to determine the precise nature of the particle and its significance for our understanding of the universe. Are its properties as expected for the long-sought Higgs boson, the final missing ingredient in the Standard Model of particle physics? Or is it something more exotic? The Standard Model describes the fundamental particles from which we, and all visible matter in the universe, are made, and the forces acting between them. All the matter that we can see, however, appears to be no more than about 4% of the total. A more exotic version of the Higgs particle could be a bridge to understanding the 96% of the universe that remains obscure also know as dark matter and dark energy. Positive identification of the new particle’s characteristics will take considerable time and data. But whatever forms the Higgs particle takes; our knowledge of the fundamental structure of matter is about to take a major step forward.
The introduction of Pakistan to CERN dates back to the 1960s through the late Abdus Salam, Pakistan`s only Nobel Laureate. The existence of weak neutral currents, independently predicted by Abdus Salam, Steven Weinberg and Sheldon Glashow, was confirmed by the experiments at CERN in 1973. They shared a Nobel Prize for the discovery in 1979. On the suggestion of Abdus Salam, an informal cooperation between Pakistan and CERN was established. Owen Lock from CERN and Pakistan Atomic energy Commission (PAEC) played an important role in this setup. In the meantime, theoretical physicists from Pakistan had the opportunity to work at CERN through short-term visits. It was in 1997 when an agreement worth one million Swiss francs was signed between PAEC and CERN for the construction of eight magnet supports for CMS detector.
In year 2000 another agreement covering the construction of resistive plate chambers (RPC) for the CMS muon system was signed. RPCs are electronic devices used for the identification and precise measurement of momentum of muons. National centre for physics (NCP) in Islamabad is a part of LHC computing grid project, which means that NCP is a place to provide computers and software structure to perform sophisticated data analysis. Pakistan has not only made financial contribution, worth $10 million, but also has provided manpower during the commissioning of the CMS detector. This is worth mentioning that other Pakistani postdocs and students associated with the US and European institutions are contributing towards making the whole project a success story. A few of them are University of Oregon, University of Oklahoma, SUNY Stony Brook and University of Texas Dallas.
 The Quantum Frontier: The Large Hadron Collider by Don Lincoln
Thanks to Dr. Mansoora Shamim for this article. About her:
Dr. Mansoora Shamim is an Ahmadi Muslim scientist working at CERN in Geneva Switzerland. Born is Muzaffargarh, Pakistan, she got her bachelors degree from Lahore college for Women in 1995 with a Rolls of Honor, a masters degree in Physics from the University of Punjab, Lahore securing second position among all the students. Following the guidance provided by Prof. Dr Mujahid Kamran (a close friend of late Dr. Abdus Salam) she went to the Abdus Salam ICTP, Trieste in 1999, where she was awarded a one year scholarship to complete the post graduate diploma course in theoretical high energy physics.
In 2001, she joined graduate school at Kansas State University in Manhattan, Kansas and obtained a Ph.D degree in experimental particle physics in 2008. During her Ph.D, Dr. Shamim analyzed the data collected by the D0 experiment at Fermilab, Tevatron located in the west suburbs of Chicago, IL. Since, July 2008, Dr. Shamim has been working as a post doc for the university of Oregon in Eugene. She is currently based at CERN working on ATLAS experiment, where she has served as the responsible person for data quality monitoring for tau trigger from 2009-2010.
From March 2010-feb 2012, she has served as deputy convener as well as the convener of the tau trigger group. The data used in the discovery of Higgs like boson were collected using tau triggers in three different channels.
Dr. Shamim is currently involved in the search for quantum black holes in the data collected by ATLAS in 2012.