Particle physics is a captivating field that aims to understand the fundamental building blocks of the universe. Scientists from the renowned CMS Collaboration have conducted an intriguing research study on the angular analysis of the decay B0 to K*0 mu mu from pp collisions at sqrt(s) = 8 TeV. This ground-breaking research, carried out at the Large Hadron Collider (LHC), provides valuable insights into the behavior of subatomic particles and tests the predictions of the standard model.

Before we delve into the details of this research, let’s first understand what angular analysis is and why it plays a crucial role in unraveling the mysteries of particle decays.

What is the Angular Analysis of the Decay B0 to K*0 mu mu?

Angular analysis is a crucial technique employed in particle physics to study the angular distributions of particles produced in a decay process. By analyzing the particle angles, scientists can extract valuable information about the internal dynamics of the decaying system.

In this particular study, the CMS Collaboration focused on the decay process of a B0 meson (composed of a bottom quark and an antibottom quark) decaying into a K*0(892) meson (composed of an up quark and an anti-strange quark) and two muons. The B0 meson is extremely unstable and quickly decays into other particles, making it a fascinating subject of investigation.

The researchers collected an impressive amount of data, corresponding to an integrated luminosity of 20.5 inverse femtobarns, during proton-proton (pp) collisions at a center-of-mass energy of 8 TeV. These collisions occur within the LHC, a powerful particle accelerator that accelerates and collides protons at incredibly high speeds.

Now that we have gained a basic understanding of the research topic, let’s explore the measurements obtained from the angular analysis of the B0 to K*0 mu mu decay.

What are the Measurements Obtained from the Analysis?

The researchers meticulously analyzed the angular distributions and the differential branching fraction of the B0 to K*0 mu mu decay using their extensive dataset. From a staggering 1430 signal decays, they obtained crucial measurements that shed light on the behavior of particles involved in the decay process.

Forward-Backward Asymmetry of the Muons

One of the key measurements obtained from this analysis is the forward-backward asymmetry of the muons. This asymmetry quantifies the difference in the angular distributions of the muons produced in the forward direction (opposite to the initial proton beam) and the backward direction.

The forward-backward asymmetry provides insights into the nature of the underlying forces and interactions governing the decay process. It allows scientists to discern asymmetries caused by potential new physics beyond the predictions of the standard model.

By carefully studying the angular distribution of the muons, the CMS Collaboration determined the forward-backward asymmetry as a function of the dimuon invariant mass squared. This detailed measurement enables them to probe the behavior of the particles involved at different energy scales, providing essential information to verify or challenge existing theories.

K*0(892) Longitudinal Polarization Fraction

Another important measurement obtained from this analysis is the K*0(892) longitudinal polarization fraction. This fraction indicates the percentage of K*0(892) mesons that are longitudinally polarized during the decay process.

Understanding the polarization of particles is essential as it reveals significant clues about the underlying physics principles at play. The longitudinal polarization fraction measurement helps scientists determine the relative contributions of various decay mechanisms and assess the agreement with theoretical predictions.

By investigating the angular distributions of the decay products, the CMS Collaboration determined the K*0(892) longitudinal polarization fraction as a function of the dimuon invariant mass squared. This measurement enables them to scrutinize the polarization behavior at different energy regimes and enhance our understanding of particle interactions.

Differential Branching Fraction

Additionally, the researchers calculated the differential branching fraction of the B0 to K*0(892) mu mu decay as a function of the dimuon invariant mass squared. The branching fraction represents the probability of a specific decay mode occurring compared to all possible decay modes.

Measuring the differential branching fraction allows scientists to compare the observed decay rate with theoretical predictions derived from the standard model. Any deviations between the measurements and the predictions could indicate the presence of new physics phenomena.

Now that we have explored the measurements obtained from the angular analysis, let’s delve into a captivating question: how do these measurements compare to the predictions of the standard model?

How do the Measurements Compare to Standard Model Predictions?

Validating the predictions of the standard model is crucial for physicists to ensure its accuracy in describing the behavior of subatomic particles. The measurements obtained from the angular analysis of the B0 to K*0 mu mu decay play a vital role in testing the predictions of this widely accepted theoretical framework.

Remarkably, the measurements conducted by the CMS Collaboration are among the most precise to date, highlighting the incredible advancements achieved in experimental techniques and data analysis. These precise measurements provide a stringent test of the standard model’s predictions and allow scientists to explore potential deviations that could point towards new physics phenomena.

So, how did the measurements fare against the predictions of the standard model? Astonishingly, the measurements obtained from the angular analysis of the B0 to K*0 mu mu decay are in good agreement with the predictions derived from the standard model.

This agreement between the experimental measurements and theoretical predictions is not to be taken for granted. It serves as a testament to the remarkable success of the standard model in describing the fundamental forces and particles that constitute our universe.

Unveiling the Secrets of Particle Physics

The angular analysis of the decay B0 to K*0 mu mu, conducted by the CMS Collaboration, is a significant step towards unraveling the secrets of particle physics. The meticulous measurements obtained from this analysis provide valuable insights into the behavior of particles involved in the decay process.

By investigating the forward-backward asymmetry of the muons, the K*0(892) longitudinal polarization fraction, and the differential branching fraction, scientists can scrutinize the predictions of the standard model and search for hints of new physics phenomena. The agreement between the measurements and the standard model predictions showcases the model’s efficacy in explaining the behavior of subatomic particles.

The remarkable advancements in experimental techniques, coupled with the extraordinary capabilities of the LHC, have opened up new avenues for scientific exploration. The angular analysis of particle decays allows researchers to peer into the intricate world of subatomic particles and deepen our understanding of the fundamental forces that shape our universe.

Through this groundbreaking research, we move one step closer to unlocking the mysteries of the cosmos and forging the future of particle physics.

Sources:
https://arxiv.org/abs/1507.08126