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Belle II Experiment: Unraveling the Mysteries of B Mesons

Scientists study B mesons to understand matter, anti-matter, and the universe's fundamental forces.

Belle II Collaboration, I. Adachi, L. Aggarwal, H. Ahmed, N. Akopov, M. Alhakami, A. Aloisio, N. Althubiti, N. Anh Ky, D. M. Asner, H. Atmacan, V. Aushev, M. Aversano, R. Ayad, V. Babu, N. K. Baghel, P. Bambade, Sw. Banerjee, M. Barrett, M. Bartl, J. Baudot, A. Baur, A. Beaubien, J. Becker, J. V. Bennett, V. Bertacchi, M. Bertemes, E. Bertholet, M. Bessner, S. Bettarini, B. Bhuyan, D. Biswas, A. Bobrov, D. Bodrov, A. Bolz, A. Bondar, J. Borah, A. Boschetti, A. Bozek, M. Bračko, P. Branchini, R. A. Briere, T. E. Browder, A. Budano, S. Bussino, Q. Campagna, M. Campajola, G. Casarosa, C. Cecchi, J. Cerasoli, M. -C. Chang, P. Chang, R. Cheaib, P. Cheema, B. G. Cheon, K. Chilikin, K. Chirapatpimol, H. -E. Cho, K. Cho, S. -J. Cho, S. -K. Choi, S. Choudhury, J. Cochran, L. Corona, J. X. Cui, E. De La Cruz-Burelo, S. A. De La Motte, G. De Nardo, G. De Pietro, R. de Sangro, M. Destefanis, S. Dey, F. Di Capua, J. Dingfelder, Z. Doležal, I. Domínguez Jiménez, T. V. Dong, X. Dong, M. Dorigo, D. Dossett, K. Dugic, G. Dujany, P. Ecker, J. Eppelt, P. Feichtinger, T. Ferber, T. Fillinger, C. Finck, G. Finocchiaro, A. Fodor, F. Forti, B. G. Fulsom, A. Gabrielli, E. Ganiev, M. Garcia-Hernandez, R. Garg, G. Gaudino, V. Gaur, A. Gaz, A. Gellrich, G. Ghevondyan, D. Ghosh, H. Ghumaryan, G. Giakoustidis, R. Giordano, A. Giri, P. Gironella Gironell, A. Glazov, B. Gobbo, R. Godang, O. Gogota, P. Goldenzweig, W. Gradl, E. Graziani, D. Greenwald, Z. Gruberová, Y. Guan, K. Gudkova, I. Haide, T. Hara, C. Harris, K. Hayasaka, S. Hazra, C. Hearty, M. T. Hedges, A. Heidelbach, I. Heredia de la Cruz, M. Hernández Villanueva, T. Higuchi, M. Hoek, M. Hohmann, R. Hoppe, P. Horak, C. -L. Hsu, T. Humair, T. Iijima, K. Inami, N. Ipsita, A. Ishikawa, R. Itoh, M. Iwasaki, D. Jacobi, W. W. Jacobs, E. -J. Jang, Y. Jin, A. Johnson, H. Junkerkalefeld, M. Kaleta, A. B. Kaliyar, J. Kandra, F. Keil, C. Ketter, C. Kiesling, C. -H. Kim, D. Y. Kim, J. -Y. Kim, K. -H. Kim, Y. -K. Kim, K. Kinoshita, P. Kodyš, T. Koga, S. Kohani, K. Kojima, A. Korobov, S. Korpar, E. Kovalenko, R. Kowalewski, P. Križan, P. Krokovny, T. Kuhr, Y. Kulii, R. Kumar, K. Kumara, T. Kunigo, A. Kuzmin, Y. -J. Kwon, S. Lacaprara, K. Lalwani, T. Lam, L. Lanceri, J. S. Lange, T. S. Lau, M. Laurenza, R. Leboucher, F. R. Le Diberder, M. J. Lee, C. Lemettais, P. Leo, L. K. Li, Q. M. Li, W. Z. Li, Y. Li, Y. B. Li, Y. P. Liao, J. Libby, J. Lin, S. Lin, M. H. Liu, Q. Y. Liu, Z. Q. Liu, D. Liventsev, S. Longo, T. Lueck, C. Lyu, Y. Ma, C. Madaan, M. Maggiora, S. P. Maharana, R. Maiti, G. Mancinelli, R. Manfredi, E. Manoni, M. Mantovano, D. Marcantonio, S. Marcello, C. Marinas, C. Martellini, A. Martens, A. Martini, T. Martinov, L. Massaccesi, M. Masuda, K. Matsuoka, D. Matvienko, S. K. Maurya, M. Maushart, J. A. McKenna, F. Meier, D. Meleshko, M. Merola, C. Miller, M. Mirra, S. Mitra, K. Miyabayashi, H. Miyake, G. B. Mohanty, S. Mondal, S. Moneta, H. -G. Moser, R. Mussa, I. Nakamura, M. Nakao, Y. Nakazawa, M. Naruki, Z. Natkaniec, A. Natochii, M. Nayak, G. Nazaryan, M. Neu, S. Nishida, S. Ogawa, R. Okubo, H. Ono, Y. Onuki, G. Pakhlova, S. Pardi, K. Parham, H. Park, J. Park, K. Park, S. -H. Park, A. Passeri, S. Patra, T. K. Pedlar, I. Peruzzi, R. Peschke, R. Pestotnik, L. E. Piilonen, P. L. M. Podesta-Lerma, T. Podobnik, S. Pokharel, C. Praz, S. Prell, E. Prencipe, M. T. Prim, H. Purwar, S. Raiz, K. Ravindran, J. U. Rehman, M. Reif, S. Reiter, M. Remnev, L. Reuter, D. Ricalde Herrmann, I. Ripp-Baudot, G. Rizzo, M. Roehrken, J. M. Roney, A. Rostomyan, N. Rout, Y. Sakai, D. A. Sanders, S. Sandilya, L. Santelj, V. Savinov, B. Scavino, C. Schwanda, A. J. Schwartz, Y. Seino, A. Selce, K. Senyo, J. Serrano, M. E. Sevior, C. Sfienti, W. Shan, X. D. Shi, T. Shillington, J. -G. Shiu, D. Shtol, B. Shwartz, A. Sibidanov, F. Simon, J. Skorupa, R. J. Sobie, M. Sobotzik, A. Soffer, A. Sokolov, E. Solovieva, S. Spataro, B. Spruck, W. Song, M. Starič, P. Stavroulakis, S. Stefkova, R. Stroili, J. Strube, M. Sumihama, K. Sumisawa, N. Suwonjandee, H. Svidras, M. Takizawa, U. Tamponi, K. Tanida, F. Tenchini, A. Thaller, O. Tittel, R. Tiwary, E. Torassa, K. Trabelsi, I. Tsaklidis, I. Ueda, T. Uglov, K. Unger, Y. Unno, K. Uno, S. Uno, P. Urquijo, Y. Ushiroda, S. E. Vahsen, R. van Tonder, K. E. Varvell, M. Veronesi, A. Vinokurova, V. S. Vismaya, L. Vitale, V. Vobbilisetti, R. Volpe, M. Wakai, S. Wallner, M. -Z. Wang, A. Warburton, M. Watanabe, S. Watanuki, C. Wessel, E. Won, X. P. Xu, B. D. Yabsley, S. Yamada, W. Yan, J. Yelton, J. H. Yin, K. Yoshihara, J. Yuan, Y. Yusa, L. Zani, V. Zhilich, J. S. Zhou, Q. D. Zhou, L. Zhu, R. Žlebčík

― 7 min read

Decoding B Mesons at Decoding B Mesons at Belle II anti-matter interactions. Belle II reveals secrets of matter and
Table of Contents

The Belle II experiment is a major scientific undertaking based at the SuperKEKB accelerator in Japan. It's part of the ongoing quest to understand the very building blocks of our universe. With a focus on studying particles known as B Mesons, researchers aim to unravel mysteries related to matter, anti-matter, and the fundamental forces of nature.

What Are B Mesons Anyway?

B mesons are particles made up of a bottom quark and an anti-quark. To understand what that means, picture a tiny ball made up of two types of building blocks—one being a bottom quark, whose name sounds like it was created during a particularly bad dad joke! These particles are of great interest because they provide clues about how the universe behaves at a fundamental level.

The SuperKEKB Accelerator

The SuperKEKB accelerator is a pretty impressive piece of machinery. Imagine a racetrack for particles, where they zip around at mind-boggling speeds—about 3 million times faster than a speeding bullet! This accelerator collides electron and positron beams to create high-energy conditions, perfect for producing B mesons and studying them.

Why Study CP Violation?

Now, what’s CP violation, and why do scientists care about it? CP violation refers to the differences in how matter and anti-matter behave. In simple terms, it helps explain why we have more matter than anti-matter in our universe. If they were created equally, everything would have annihilated itself and left behind a barren wasteland. So, by studying how B mesons decay—basically how they break apart—scientists can learn more about this mysterious imbalance.

Longitudinal Polarization and Branching Fractions

In the realm of particle physics, terms like "branching fraction" and "longitudinal polarization" can sound complicated. Let’s break it down. The branching fraction tells us how often a specific decay process occurs compared to all possible processes. It’s like knowing how often you choose pizza over salad for dinner. Longitudinal polarization indicates how the particles spin in a particular alignment. If you think of it like a dancer, it tells us if they are doing a twirl or sliding across the floor in a certain direction!

Collecting Data

To get all this juicy information about B mesons, Belle II collected data by smashing particles together from 2019 to 2022. The experiment observed many different types of decays, measuring how often each one occurred. The results are akin to taking a deep dive into a pool filled with data—except this pool is more like an ocean, and scientists are trying to spot fish that are hard to see!

The Analysis Process

After all the data collection, the next challenge is analyzing it. Scientists need to sift through vast amounts of information, much like a librarian trying to find one specific book in a gigantic library. They look for interesting patterns and anomalies that might indicate new physics beyond the standard model—the conventional theory explaining particle interactions.

Unraveling the CKM Matrix

One of the big goals of this research is to get a clearer picture of the CKM matrix, which is a fancy term for understanding how different quarks mix and interact. It’s like learning the secret handshake among tiny particles. By figuring out the angles and sides of this matrix—just as one would measure a triangle—scientists can gain insights into potential new physics.

Measuring CP Violation Parameters

To quantify CP violation, researchers measure several parameters to see how B mesons decay over time. Think of it as timing a race: how long it takes for one type of B meson to decay compared to another. By observing these time-dependent changes, scientists can draw conclusions about the behavior of these particles.

The Role of Simulation

Belle II relies heavily on computer simulations to interpret the data. This is like having a virtual laboratory where scientists can test their hypotheses without risking spilled coffee—because trust me, no one wants to clean that mess up in a real science lab! These simulations help refine detection methods and improve the accuracy of measurements.

Event Selection and Reconstruction

After collecting data, the next step is to select specific events of interest. Researchers want to focus on high-quality events that yield the best insights. This is similar to being at a concert and trying to capture the best moments on your phone while avoiding blurry images. After selecting these events, the next step is to reconstruct what actually happened during the collision, peeling back layers of complexity.

Tackling Background Noise

Just like in a noisy café, background noise can interfere with what you're trying to hear. In particle physics, unwanted events can obscure the signals researchers want to study. Belle II employs sophisticated techniques to minimize this background noise, ensuring that valuable data doesn’t get lost in the ruckus.

The Fitting Procedure

Once the data is in hand, scientists use statistical techniques to fit the observed data to theoretical models. This fitting process is crucial in extracting meaningful parameters from the chaotic particle collisions. It’s akin to using a puzzle to fit together different pieces to complete the big picture of how B mesons behave.

Understanding the Systematic Uncertainties

Every measurement comes with uncertainty. Scientists have to account for various types of errors that can pop up in their analysis—like reading a clock but not being sure if it’s showing the correct time. By identifying and quantifying these uncertainties, researchers can provide more accurate results and conclusions.

Isospin Analysis

The results from Belle II also allow researchers to conduct isospin analyses, which help to further constrain CKM parameters. This is a bit like using detective work to figure out the relationships between particles, closely examining how they interact and the roles they play in the bigger picture of particle physics.

The Results

After conducting extensive analysis, the Belle II experiment reported its findings in terms of branching fractions, polarization, and CP violation parameters. The results were not only exciting on their own but also played a significant role in advancing the field of particle physics—offering valuable insights into both standard and non-standard model physics.

Future Directions

The journey doesn’t stop here! With new data set to be collected, combined with the findings from Belle II, there's hope for even deeper insights into the realm of particle physics. Researchers are eager to continue exploring the hidden complexities of the universe, including more about matter, anti-matter, and how everything fits together.

The Importance of Collaboration

The Belle II experiment is not a solo endeavor. It involves the efforts of scientists from around the globe, collaborating to push the boundaries of knowledge. It’s like a global concert, where each musician plays their part to create a harmonious symphony of scientific discovery!

Conclusion

The Belle II experiment has emerged as an essential platform for studying B mesons and the profound questions surrounding our universe. By combining cutting-edge technology, meticulous data collection, and collaboration, scientists continue to make strides in understanding the fundamental processes that govern particle interactions. Who knows? Maybe one day, we’ll finally understand why the universe leans more toward matter than anti-matter, or even discover something completely unexpected. So, keep your eyes on the stars and your minds open, as the journey through the world of particle physics is anything but boring!

Original Source

Title: Measurement of the branching fraction, polarization, and time-dependent $CP$ asymmetry in $B^0 \to \rho^+\rho^-$ decays and constraint on the CKM angle $\phi_2$

Abstract: We present a measurement of the branching fraction and fraction of longitudinal polarization of $B^0 \to \rho^+ \rho^-$ decays, which have two $\pi^0$'s in the final state. We also measure time-dependent $CP$ violation parameters for decays into longitudinally polarized $\rho^+ \rho^-$ pairs. This analysis is based on a data sample containing $(387\pm6) \times 10^6$ \BBbar pairs collected with the Belle~II detector at the SuperKEKB asymmetric-energy $e^+e^-$ collider in 2019-2022. We obtain ${B}(B^0\to\rho^+\rho^-) = (2.88 ^{+0.23}_{-0.22} {}^{+0.29}_{-0.27}) \times 10^{-5}, f_{L} = 0.921 ^{+0.024}_{-0.025} {}^{+0.017}_{-0.015}$, $S = -0.26\pm0.19\pm0.08$, and $C = -0.02\pm0.12^{+0.06}_{-0.05}$, where the first uncertainties are statistical and the second are systematic. We use these results to perform an isospin analysis to constrain the CKM angle $\phi_2$ and obtain two solutions; the result consistent with other Standard Model constraints is $\phi_2 = (92.6^{+4.5}_{-4.8})^\circ$.

Authors: Belle II Collaboration, I. Adachi, L. Aggarwal, H. Ahmed, N. Akopov, M. Alhakami, A. Aloisio, N. Althubiti, N. Anh Ky, D. M. Asner, H. Atmacan, V. Aushev, M. Aversano, R. Ayad, V. Babu, N. K. Baghel, P. Bambade, Sw. Banerjee, M. Barrett, M. Bartl, J. Baudot, A. Baur, A. Beaubien, J. Becker, J. V. Bennett, V. Bertacchi, M. Bertemes, E. Bertholet, M. Bessner, S. Bettarini, B. Bhuyan, D. Biswas, A. Bobrov, D. Bodrov, A. Bolz, A. Bondar, J. Borah, A. Boschetti, A. Bozek, M. Bračko, P. Branchini, R. A. Briere, T. E. Browder, A. Budano, S. Bussino, Q. Campagna, M. Campajola, G. Casarosa, C. Cecchi, J. Cerasoli, M. -C. Chang, P. Chang, R. Cheaib, P. Cheema, B. G. Cheon, K. Chilikin, K. Chirapatpimol, H. -E. Cho, K. Cho, S. -J. Cho, S. -K. Choi, S. Choudhury, J. Cochran, L. Corona, J. X. Cui, E. De La Cruz-Burelo, S. A. De La Motte, G. De Nardo, G. De Pietro, R. de Sangro, M. Destefanis, S. Dey, F. Di Capua, J. Dingfelder, Z. Doležal, I. Domínguez Jiménez, T. V. Dong, X. Dong, M. Dorigo, D. Dossett, K. Dugic, G. Dujany, P. Ecker, J. Eppelt, P. Feichtinger, T. Ferber, T. Fillinger, C. Finck, G. Finocchiaro, A. Fodor, F. Forti, B. G. Fulsom, A. Gabrielli, E. Ganiev, M. Garcia-Hernandez, R. Garg, G. Gaudino, V. Gaur, A. Gaz, A. Gellrich, G. Ghevondyan, D. Ghosh, H. Ghumaryan, G. Giakoustidis, R. Giordano, A. Giri, P. Gironella Gironell, A. Glazov, B. Gobbo, R. Godang, O. Gogota, P. Goldenzweig, W. Gradl, E. Graziani, D. Greenwald, Z. Gruberová, Y. Guan, K. Gudkova, I. Haide, T. Hara, C. Harris, K. Hayasaka, S. Hazra, C. Hearty, M. T. Hedges, A. Heidelbach, I. Heredia de la Cruz, M. Hernández Villanueva, T. Higuchi, M. Hoek, M. Hohmann, R. Hoppe, P. Horak, C. -L. Hsu, T. Humair, T. Iijima, K. Inami, N. Ipsita, A. Ishikawa, R. Itoh, M. Iwasaki, D. Jacobi, W. W. Jacobs, E. -J. Jang, Y. Jin, A. Johnson, H. Junkerkalefeld, M. Kaleta, A. B. Kaliyar, J. Kandra, F. Keil, C. Ketter, C. Kiesling, C. -H. Kim, D. Y. Kim, J. -Y. Kim, K. -H. Kim, Y. -K. Kim, K. Kinoshita, P. Kodyš, T. Koga, S. Kohani, K. Kojima, A. Korobov, S. Korpar, E. Kovalenko, R. Kowalewski, P. Križan, P. Krokovny, T. Kuhr, Y. Kulii, R. Kumar, K. Kumara, T. Kunigo, A. Kuzmin, Y. -J. Kwon, S. Lacaprara, K. Lalwani, T. Lam, L. Lanceri, J. S. Lange, T. S. Lau, M. Laurenza, R. Leboucher, F. R. Le Diberder, M. J. Lee, C. Lemettais, P. Leo, L. K. Li, Q. M. Li, W. Z. Li, Y. Li, Y. B. Li, Y. P. Liao, J. Libby, J. Lin, S. Lin, M. H. Liu, Q. Y. Liu, Z. Q. Liu, D. Liventsev, S. Longo, T. Lueck, C. Lyu, Y. Ma, C. Madaan, M. Maggiora, S. P. Maharana, R. Maiti, G. Mancinelli, R. Manfredi, E. Manoni, M. Mantovano, D. Marcantonio, S. Marcello, C. Marinas, C. Martellini, A. Martens, A. Martini, T. Martinov, L. Massaccesi, M. Masuda, K. Matsuoka, D. Matvienko, S. K. Maurya, M. Maushart, J. A. McKenna, F. Meier, D. Meleshko, M. Merola, C. Miller, M. Mirra, S. Mitra, K. Miyabayashi, H. Miyake, G. B. Mohanty, S. Mondal, S. Moneta, H. -G. Moser, R. Mussa, I. Nakamura, M. Nakao, Y. Nakazawa, M. Naruki, Z. Natkaniec, A. Natochii, M. Nayak, G. Nazaryan, M. Neu, S. Nishida, S. Ogawa, R. Okubo, H. Ono, Y. Onuki, G. Pakhlova, S. Pardi, K. Parham, H. Park, J. Park, K. Park, S. -H. Park, A. Passeri, S. Patra, T. K. Pedlar, I. Peruzzi, R. Peschke, R. Pestotnik, L. E. Piilonen, P. L. M. Podesta-Lerma, T. Podobnik, S. Pokharel, C. Praz, S. Prell, E. Prencipe, M. T. Prim, H. Purwar, S. Raiz, K. Ravindran, J. U. Rehman, M. Reif, S. Reiter, M. Remnev, L. Reuter, D. Ricalde Herrmann, I. Ripp-Baudot, G. Rizzo, M. Roehrken, J. M. Roney, A. Rostomyan, N. Rout, Y. Sakai, D. A. Sanders, S. Sandilya, L. Santelj, V. Savinov, B. Scavino, C. Schwanda, A. J. Schwartz, Y. Seino, A. Selce, K. Senyo, J. Serrano, M. E. Sevior, C. Sfienti, W. Shan, X. D. Shi, T. Shillington, J. -G. Shiu, D. Shtol, B. Shwartz, A. Sibidanov, F. Simon, J. Skorupa, R. J. Sobie, M. Sobotzik, A. Soffer, A. Sokolov, E. Solovieva, S. Spataro, B. Spruck, W. Song, M. Starič, P. Stavroulakis, S. Stefkova, R. Stroili, J. Strube, M. Sumihama, K. Sumisawa, N. Suwonjandee, H. Svidras, M. Takizawa, U. Tamponi, K. Tanida, F. Tenchini, A. Thaller, O. Tittel, R. Tiwary, E. Torassa, K. Trabelsi, I. Tsaklidis, I. Ueda, T. Uglov, K. Unger, Y. Unno, K. Uno, S. Uno, P. Urquijo, Y. Ushiroda, S. E. Vahsen, R. van Tonder, K. E. Varvell, M. Veronesi, A. Vinokurova, V. S. Vismaya, L. Vitale, V. Vobbilisetti, R. Volpe, M. Wakai, S. Wallner, M. -Z. Wang, A. Warburton, M. Watanabe, S. Watanuki, C. Wessel, E. Won, X. P. Xu, B. D. Yabsley, S. Yamada, W. Yan, J. Yelton, J. H. Yin, K. Yoshihara, J. Yuan, Y. Yusa, L. Zani, V. Zhilich, J. S. Zhou, Q. D. Zhou, L. Zhu, R. Žlebčík

Last Update: 2024-12-27 00:00:00

Language: English

Source URL: https://arxiv.org/abs/2412.19624

Source PDF: https://arxiv.org/pdf/2412.19624

Licence: https://creativecommons.org/licenses/by/4.0/

Changes: This summary was created with assistance from AI and may have inaccuracies. For accurate information, please refer to the original source documents linked here.

Thank you to arxiv for use of its open access interoperability.

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