⚛️ high-energy experiments

Comprehensive analysis of the $B^0\to K^{*0}\mu^+\mu^-$ decay

Using 8.4 fb $^{-1}$ of LHCb proton-proton collision data, this paper presents a comprehensive analysis of the $B^0\to K^{*0}\mu^+\mu^-$ decay that includes the first full set of S-wave observables and muon mass effects, confirming that the measured $CP$-averaged observables and branching fractions continue to exhibit tensions with Standard Model predictions.

Original authors: LHCb collaboration, R. Aaij, A. S. W. Abdelmotteleb, C. Abellan Beteta, F. Abudinén, T. Ackernley, A. A. Adefisoye, B. Adeva, M. Adinolfi, P. Adlarson, C. Agapopoulou, C. A. Aidala, Z. Ajaltouni, S. ALHCb collaboration, R. Aaij, A. S. W. Abdelmotteleb, C. Abellan Beteta, F. Abudinén, T. Ackernley, A. A. Adefisoye, B. Adeva, M. Adinolfi, P. Adlarson, C. Agapopoulou, C. A. Aidala, Z. Ajaltouni, S. Akar, K. Akiba, P. Albicocco, J. Albrecht, R. Aleksiejunas, F. Alessio, P. Alvarez Cartelle, R. Amalric, S. Amato, J. L. Amey, Y. Amhis, L. An, L. Anderlini, M. Andersson, P. Andreola, M. Andreotti, S. Andres Estrada, A. Anelli, D. Ao, C. Arata, F. Archilli, Z. Areg, M. Argenton, S. Arguedas Cuendis, L. Arnone, A. Artamonov, M. Artuso, E. Aslanides, R. Ataíde Da Silva, M. Atzeni, B. Audurier, J. A. Authier, D. Bacher, I. Bachiller Perea, S. Bachmann, M. Bachmayer, J. J. Back, P. Baladron Rodriguez, V. Balagura, A. Balboni, W. Baldini, Z. Baldwin, L. Balzani, H. Bao, J. Baptista de Souza Leite, C. Barbero Pretel, M. Barbetti, I. R. Barbosa, R. J. Barlow, M. Barnyakov, S. Barsuk, W. Barter, J. Bartz, S. Bashir, B. Batsukh, P. B. Battista, A. Bay, A. Beck, M. Becker, F. Bedeschi, I. B. Bediaga, N. A. Behling, S. Belin, A. Bellavista, K. Belous, I. Belov, I. Belyaev, G. Benane, G. Bencivenni, E. Ben-Haim, A. Berezhnoy, R. Bernet, S. Bernet Andres, A. Bertolin, F. Betti, J. Bex, O. Bezshyyko, S. Bhattacharya, J. Bhom, M. S. Bieker, N. V. Biesuz, A. Biolchini, M. Birch, F. C. R. Bishop, A. Bitadze, A. Bizzeti, T. Blake, F. Blanc, J. E. Blank, S. Blusk, V. Bocharnikov, J. A. Boelhauve, O. Boente Garcia, T. Boettcher, A. Bohare, A. Boldyrev, C. Bolognani, R. Bolzonella, R. B. Bonacci, N. Bondar, A. Bordelius, F. Borgato, S. Borghi, M. Borsato, J. T. Borsuk, E. Bottalico, S. A. Bouchiba, M. Bovill, T. J. V. Bowcock, A. Boyer, C. Bozzi, J. D. Brandenburg, A. Brea Rodriguez, N. Breer, J. Brodzicka, J. Brown, D. Brundu, E. Buchanan, M. Burgos Marcos, A. T. Burke, C. Burr, C. Buti, J. S. Butter, J. Buytaert, W. Byczynski, S. Cadeddu, H. Cai, Y. Cai, A. Caillet, R. Calabrese, S. Calderon Ramirez, L. Calefice, M. Calvi, M. Calvo Gomez, P. Camargo Magalhaes, J. I. Cambon Bouzas, P. Campana, A. F. Campoverde Quezada, Y. Cao, S. Capelli, M. Caporale, L. Capriotti, R. Caravaca-Mora, A. Carbone, L. Carcedo Salgado, R. Cardinale, A. Cardini, P. Carniti, L. Carus, A. Casais Vidal, R. Caspary, G. Casse, M. Cattaneo, G. Cavallero, V. Cavallini, S. Celani, I. Celestino, S. Cesare, A. J. Chadwick, I. Chahrour, H. Chang, M. Charles, Ph. Charpentier, E. Chatzianagnostou, R. Cheaib, M. Chefdeville, C. Chen, J. Chen, S. Chen, Z. Chen, A. Chen Hu, M. Cherif, A. Chernov, S. Chernyshenko, X. Chiotopoulos, V. Chobanova, M. Chrzaszcz, A. Chubykin, V. Chulikov, P. Ciambrone, X. Cid Vidal, G. Ciezarek, P. Cifra, P. E. L. Clarke, M. Clemencic, H. V. Cliff, J. Closier, C. Cocha Toapaxi, V. Coco, J. Cogan, E. Cogneras, L. Cojocariu, S. Collaviti, P. Collins, T. Colombo, M. Colonna, A. Comerma-Montells, L. Congedo, J. Connaughton, A. Contu, N. Cooke, G. Cordova, C. Coronel, I. Corredoira, A. Correia, G. Corti, J. Cottee Meldrum, B. Couturier, D. C. Craik, M. Cruz Torres, E. Curras Rivera, R. Currie, C. L. Da Silva, S. Dadabaev, X. Dai, E. Dall'Occo, J. Dalseno, C. D'Ambrosio, J. Daniel, G. Darze, A. Davidson, J. E. Davies, O. De Aguiar Francisco, C. De Angelis, F. De Benedetti, J. de Boer, K. De Bruyn, S. De Capua, M. De Cian, U. De Freitas Carneiro Da Graca, E. De Lucia, J. M. De Miranda, L. De Paula, M. De Serio, P. De Simone, F. De Vellis, J. A. de Vries, F. Debernardis, D. Decamp, S. Dekkers, L. Del Buono, B. Delaney, H. -P. Dembinski, J. Deng, V. Denysenko, O. Deschamps, F. Dettori, B. Dey, P. Di Nezza, I. Diachkov, S. Didenko, S. Ding, Y. Ding, L. Dittmann, V. Dobishuk, A. D. Docheva, A. Doheny, C. Dong, A. M. Donohoe, F. Dordei, A. C. dos Reis, A. D. Dowling, L. Dreyfus, W. Duan, P. Duda, L. Dufour, V. Duk, P. Durante, M. M. Duras, J. M. Durham, O. D. Durmus, A. Dziurda, A. Dzyuba, S. Easo, E. Eckstein, U. Egede, A. Egorychev, V. Egorychev, S. Eisenhardt, E. Ejopu, L. Eklund, M. Elashri, D. Elizondo Blanco, J. Ellbracht, S. Ely, A. Ene, J. Eschle, S. Esen, T. Evans, F. Fabiano, S. Faghih, L. N. Falcao, B. Fang, R. Fantechi, L. Fantini, M. Faria, K. Farmer, F. Fassin, D. Fazzini, L. Felkowski, C. Feng, M. Feng, A. Fernandez Casani, M. Fernandez Gomez, A. D. Fernez, F. Ferrari, F. Ferreira Rodrigues, M. Ferrillo, M. Ferro-Luzzi, S. Filippov, R. A. Fini, M. Fiorini, M. Firlej, K. L. Fischer, D. S. Fitzgerald, C. Fitzpatrick, T. Fiutowski, F. Fleuret, A. Fomin, M. Fontana, L. A. Foreman, R. Forty, D. Foulds-Holt, V. Franco Lima, M. Franco Sevilla, M. Frank, E. Franzoso, G. Frau, C. Frei, D. A. Friday, J. Fu, Q. Führing, T. Fulghesu, G. Galati, M. D. Galati, A. Gallas Torreira, D. Galli, S. Gambetta, M. Gandelman, P. Gandini, B. Ganie, H. Gao, R. Gao, T. Q. Gao, Y. Gao, Y. Gao, Y. Gao, L. M. Garcia Martin, P. Garcia Moreno, J. García Pardiñas, P. Gardner, L. Garrido, C. Gaspar, A. Gavrikov, L. L. Gerken, E. Gersabeck, M. Gersabeck, T. Gershon, S. Ghizzo, Z. Ghorbanimoghaddam, F. I. Giasemis, V. Gibson, H. K. Giemza, A. L. Gilman, M. Giovannetti, A. Gioventù, L. Girardey, M. A. Giza, F. C. Glaser, V. V. Gligorov, C. Göbel, L. Golinka-Bezshyyko, E. Golobardes, D. Golubkov, A. Golutvin, S. Gomez Fernandez, W. Gomulka, F. Goncalves Abrantes, I. Gonçales Vaz, M. Goncerz, G. Gong, J. A. Gooding, I. V. Gorelov, C. Gotti, E. Govorkova, J. P. Grabowski, L. A. Granado Cardoso, E. Graugés, E. Graverini, L. Grazette, G. Graziani, A. T. Grecu, N. A. Grieser, L. Grillo, S. Gromov, C. Gu, M. Guarise, L. Guerry, A. -K. Guseinov, E. Gushchin, Y. Guz, T. Gys, K. Habermann, T. Hadavizadeh, C. Hadjivasiliou, G. Haefeli, C. Haen, S. Haken, G. Hallett, P. M. Hamilton, J. Hammerich, Q. Han, X. Han, S. Hansmann-Menzemer, L. Hao, N. Harnew, T. J. Harris, M. Hartmann, S. Hashmi, J. He, A. Hedes, F. Hemmer, C. Henderson, R. Henderson, R. D. L. Henderson, A. M. Hennequin, K. Hennessy, L. Henry, J. Herd, P. Herrero Gascon, J. Heuel, A. Heyn, A. Hicheur, G. Hijano Mendizabal, J. Horswill, R. Hou, Y. Hou, D. C. Houston, N. Howarth, W. Hu, X. Hu, W. Hulsbergen, R. J. Hunter, M. Hushchyn, D. Hutchcroft, M. Idzik, D. Ilin, P. Ilten, A. Iniukhin, A. Iohner, A. Ishteev, K. Ivshin, H. Jage, S. J. Jaimes Elles, S. Jakobsen, T. Jakoubek, E. Jans, B. K. Jashal, A. Jawahery, C. Jayaweera, V. Jevtic, Z. Jia, E. Jiang, X. Jiang, Y. Jiang, Y. J. Jiang, E. Jimenez Moya, N. Jindal, M. John, A. John Rubesh Rajan, D. Johnson, C. R. Jones, S. Joshi, B. Jost, J. Juan Castella, N. Jurik, I. Juszczak, K. Kalecinska, D. Kaminaris, S. Kandybei, M. Kane, Y. Kang, C. Kar, M. Karacson, A. Kauniskangas, J. W. Kautz, M. K. Kazanecki, F. Keizer, M. Kenzie, T. Ketel, B. Khanji, A. Kharisova, S. Kholodenko, G. Khreich, T. Kirn, V. S. Kirsebom, O. Kitouni, S. Klaver, N. Kleijne, D. Klekots, K. Klimaszewski, M. R. Kmiec, T. Knospe, R. Kolb, S. Koliiev, L. Kolk, A. Konoplyannikov, P. Kopciewicz, P. Koppenburg, A. Korchin, M. Korolev, I. Kostiuk, O. Kot, S. Kotriakhova, E. Kowalczyk, A. Kozachuk, P. Kravchenko, L. Kravchuk, O. Kravcov, M. Kreps, P. Krokovny, W. Krupa, W. Krzemien, O. Kshyvanskyi, S. Kubis, M. Kucharczyk, V. Kudryavtsev, E. Kulikova, A. Kupsc, V. Kushnir, B. Kutsenko, J. Kvapil, I. Kyryllin, D. Lacarrere, P. Laguarta Gonzalez, A. Lai, A. Lampis, D. Lancierini, C. Landesa Gomez, J. J. Lane, G. Lanfranchi, C. Langenbruch, J. Langer, T. Latham, F. Lazzari, C. Lazzeroni, R. Le Gac, H. Lee, R. Lefèvre, A. Leflat, S. Legotin, M. Lehuraux, E. Lemos Cid, O. Leroy, T. Lesiak, E. D. Lesser, B. Leverington, A. Li, C. Li, C. Li, H. Li, J. Li, K. Li, L. Li, M. Li, P. Li, P. -R. Li, Q. Li, T. Li, T. Li, Y. Li, Y. Li, Y. Li, Z. Lian, Q. Liang, X. Liang, Z. Liang, S. Libralon, A. Lightbody, C. Lin, T. Lin, R. Lindner, H. Linton, R. Litvinov, D. Liu, F. L. Liu, G. Liu, K. Liu, S. Liu, W. Liu, Y. Liu, Y. Liu, Y. L. Liu, G. Loachamin Ordonez, I. Lobo, A. Lobo Salvia, A. Loi, T. Long, F. C. L. Lopes, J. H. Lopes, A. Lopez Huertas, C. Lopez Iribarnegaray, S. López Soliño, Q. Lu, C. Lucarelli, D. Lucchesi, M. Lucio Martinez, Y. Luo, A. Lupato, E. Luppi, K. Lynch, S. Lyu, X. -R. Lyu, G. M. Ma, H. Ma, S. Maccolini, F. Machefert, F. Maciuc, B. Mack, I. Mackay, L. M. Mackey, L. R. Madhan Mohan, M. J. Madurai, D. Magdalinski, D. Maisuzenko, J. J. Malczewski, S. Malde, L. Malentacca, A. Malinin, T. Maltsev, G. Manca, G. Mancinelli, C. Mancuso, R. Manera Escalero, F. M. Manganella, D. Manuzzi, D. Marangotto, J. F. Marchand, R. Marchevski, U. Marconi, E. Mariani, S. Mariani, C. Marin Benito, J. Marks, A. M. Marshall, L. Martel, G. Martelli, G. Martellotti, L. Martinazzoli, M. Martinelli, D. Martinez Gomez, D. Martinez Santos, F. Martinez Vidal, A. Martorell i Granollers, A. Massafferri, R. Matev, A. Mathad, V. Matiunin, C. Matteuzzi, K. R. Mattioli, A. Mauri, E. Maurice, J. Mauricio, P. Mayencourt, J. Mazorra de Cos, M. Mazurek, M. McCann, N. T. McHugh, A. McNab, R. McNulty, B. Meadows, S. E. R. Medaer, G. Meier, D. Melnychuk, D. Mendoza Granada, P. Menendez Valdes Perez, F. M. Meng, M. Merk, A. Merli, L. Meyer Garcia, D. Miao, H. Miao, M. Mikhasenko, D. A. Milanes, A. Minotti, E. Minucci, T. Miralles, B. Mitreska, D. S. Mitzel, R. Mocanu, A. Modak, L. Moeser, R. D. Moise, E. F. Molina Cardenas, T. Mombächer, M. Monk, S. Monteil, A. Morcillo Gomez, G. Morello, M. J. Morello, M. P. Morgenthaler, A. Moro, J. Moron, W. Morren, A. B. Morris, A. G. Morris, R. Mountain, Z. Mu, E. Muhammad, F. Muheim, M. Mulder, K. Müller, F. Muñoz-Rojas, R. Murta, V. Mytrochenko, P. Naik, T. Nakada, R. Nandakumar, T. Nanut, I. Nasteva, M. Needham, E. Nekrasova, N. Neri, S. Neubert, N. Neufeld, P. Neustroev, J. Nicolini, D. Nicotra, E. M. Niel, N. Nikitin, L. Nisi, Q. Niu, P. Nogarolli, P. Nogga, C. Normand, J. Novoa Fernandez, G. Nowak, C. Nunez, H. N. Nur, A. Oblakowska-Mucha, V. 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Published 2026-07-13

📖 4 min read🧠 Deep dive

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Original authors: LHCb collaboration, R. Aaij, A. S. W. Abdelmotteleb, C. Abellan Beteta, F. Abudinén, T. Ackernley, A. A. Adefisoye, B. Adeva, M. Adinolfi, P. Adlarson, C. Agapopoulou, C. A. Aidala, Z. Ajaltouni, S. Akar, K. Akiba, P. Albicocco, J. Albrecht, R. Aleksiejunas, F. Alessio, P. Alvarez Cartelle, R. Amalric, S. Amato, J. L. Amey, Y. Amhis, L. An, L. Anderlini, M. Andersson, P. Andreola, M. Andreotti, S. Andres Estrada, A. Anelli, D. Ao, C. Arata, F. Archilli, Z. Areg, M. Argenton, S. Arguedas Cuendis, L. Arnone, A. Artamonov, M. Artuso, E. Aslanides, R. Ataíde Da Silva, M. Atzeni, B. Audurier, J. A. Authier, D. Bacher, I. Bachiller Perea, S. Bachmann, M. Bachmayer, J. J. Back, P. Baladron Rodriguez, V. Balagura, A. Balboni, W. Baldini, Z. Baldwin, L. Balzani, H. Bao, J. Baptista de Souza Leite, C. Barbero Pretel, M. Barbetti, I. R. Barbosa, R. J. Barlow, M. Barnyakov, S. Barsuk, W. Barter, J. Bartz, S. Bashir, B. Batsukh, P. B. Battista, A. Bay, A. Beck, M. Becker, F. Bedeschi, I. B. Bediaga, N. A. Behling, S. Belin, A. Bellavista, K. Belous, I. Belov, I. Belyaev, G. Benane, G. Bencivenni, E. Ben-Haim, A. Berezhnoy, R. Bernet, S. Bernet Andres, A. Bertolin, F. Betti, J. Bex, O. Bezshyyko, S. Bhattacharya, J. Bhom, M. S. Bieker, N. V. Biesuz, A. Biolchini, M. Birch, F. C. R. Bishop, A. Bitadze, A. Bizzeti, T. Blake, F. Blanc, J. E. Blank, S. Blusk, V. Bocharnikov, J. A. Boelhauve, O. Boente Garcia, T. Boettcher, A. Bohare, A. Boldyrev, C. Bolognani, R. Bolzonella, R. B. Bonacci, N. Bondar, A. Bordelius, F. Borgato, S. Borghi, M. Borsato, J. T. Borsuk, E. Bottalico, S. A. Bouchiba, M. Bovill, T. J. V. Bowcock, A. Boyer, C. Bozzi, J. D. Brandenburg, A. Brea Rodriguez, N. Breer, J. Brodzicka, J. Brown, D. Brundu, E. Buchanan, M. Burgos Marcos, A. T. Burke, C. Burr, C. Buti, J. S. Butter, J. Buytaert, W. Byczynski, S. Cadeddu, H. Cai, Y. Cai, A. Caillet, R. Calabrese, S. Calderon Ramirez, L. Calefice, M. Calvi, M. Calvo Gomez, P. Camargo Magalhaes, J. I. Cambon Bouzas, P. Campana, A. F. Campoverde Quezada, Y. Cao, S. Capelli, M. Caporale, L. Capriotti, R. Caravaca-Mora, A. Carbone, L. Carcedo Salgado, R. Cardinale, A. Cardini, P. Carniti, L. Carus, A. Casais Vidal, R. Caspary, G. Casse, M. Cattaneo, G. Cavallero, V. Cavallini, S. Celani, I. Celestino, S. Cesare, A. J. Chadwick, I. Chahrour, H. Chang, M. Charles, Ph. Charpentier, E. Chatzianagnostou, R. Cheaib, M. Chefdeville, C. Chen, J. Chen, S. Chen, Z. Chen, A. Chen Hu, M. Cherif, A. Chernov, S. Chernyshenko, X. Chiotopoulos, V. Chobanova, M. Chrzaszcz, A. Chubykin, V. Chulikov, P. Ciambrone, X. Cid Vidal, G. Ciezarek, P. Cifra, P. E. L. Clarke, M. Clemencic, H. V. Cliff, J. Closier, C. Cocha Toapaxi, V. Coco, J. Cogan, E. Cogneras, L. Cojocariu, S. Collaviti, P. Collins, T. Colombo, M. Colonna, A. Comerma-Montells, L. Congedo, J. Connaughton, A. Contu, N. Cooke, G. Cordova, C. Coronel, I. Corredoira, A. Correia, G. Corti, J. Cottee Meldrum, B. Couturier, D. C. Craik, M. Cruz Torres, E. Curras Rivera, R. Currie, C. L. Da Silva, S. Dadabaev, X. Dai, E. Dall'Occo, J. Dalseno, C. D'Ambrosio, J. Daniel, G. Darze, A. Davidson, J. E. Davies, O. De Aguiar Francisco, C. De Angelis, F. De Benedetti, J. de Boer, K. De Bruyn, S. De Capua, M. De Cian, U. De Freitas Carneiro Da Graca, E. De Lucia, J. M. De Miranda, L. De Paula, M. De Serio, P. De Simone, F. De Vellis, J. A. de Vries, F. Debernardis, D. Decamp, S. Dekkers, L. Del Buono, B. Delaney, H. -P. Dembinski, J. Deng, V. Denysenko, O. Deschamps, F. Dettori, B. Dey, P. Di Nezza, I. Diachkov, S. Didenko, S. Ding, Y. Ding, L. Dittmann, V. Dobishuk, A. D. Docheva, A. Doheny, C. Dong, A. M. Donohoe, F. Dordei, A. C. dos Reis, A. D. Dowling, L. Dreyfus, W. Duan, P. Duda, L. Dufour, V. Duk, P. Durante, M. M. Duras, J. M. Durham, O. D. Durmus, A. Dziurda, A. Dzyuba, S. Easo, E. Eckstein, U. Egede, A. Egorychev, V. Egorychev, S. Eisenhardt, E. Ejopu, L. Eklund, M. Elashri, D. Elizondo Blanco, J. Ellbracht, S. Ely, A. Ene, J. Eschle, S. Esen, T. Evans, F. Fabiano, S. Faghih, L. N. Falcao, B. Fang, R. Fantechi, L. Fantini, M. Faria, K. Farmer, F. Fassin, D. Fazzini, L. Felkowski, C. Feng, M. Feng, A. Fernandez Casani, M. Fernandez Gomez, A. D. Fernez, F. Ferrari, F. Ferreira Rodrigues, M. Ferrillo, M. Ferro-Luzzi, S. Filippov, R. A. Fini, M. Fiorini, M. Firlej, K. L. Fischer, D. S. Fitzgerald, C. Fitzpatrick, T. Fiutowski, F. Fleuret, A. Fomin, M. Fontana, L. A. Foreman, R. Forty, D. Foulds-Holt, V. Franco Lima, M. Franco Sevilla, M. Frank, E. Franzoso, G. Frau, C. Frei, D. A. Friday, J. Fu, Q. Führing, T. Fulghesu, G. Galati, M. D. Galati, A. Gallas Torreira, D. Galli, S. Gambetta, M. Gandelman, P. Gandini, B. Ganie, H. Gao, R. Gao, T. Q. Gao, Y. Gao, Y. Gao, Y. Gao, L. M. Garcia Martin, P. Garcia Moreno, J. García Pardiñas, P. Gardner, L. Garrido, C. Gaspar, A. Gavrikov, L. L. Gerken, E. Gersabeck, M. Gersabeck, T. Gershon, S. Ghizzo, Z. Ghorbanimoghaddam, F. I. Giasemis, V. Gibson, H. K. 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Kravchuk, O. Kravcov, M. Kreps, P. Krokovny, W. Krupa, W. Krzemien, O. Kshyvanskyi, S. Kubis, M. Kucharczyk, V. Kudryavtsev, E. Kulikova, A. Kupsc, V. Kushnir, B. Kutsenko, J. Kvapil, I. Kyryllin, D. Lacarrere, P. Laguarta Gonzalez, A. Lai, A. Lampis, D. Lancierini, C. Landesa Gomez, J. J. Lane, G. Lanfranchi, C. Langenbruch, J. Langer, T. Latham, F. Lazzari, C. Lazzeroni, R. Le Gac, H. Lee, R. Lefèvre, A. Leflat, S. Legotin, M. Lehuraux, E. Lemos Cid, O. Leroy, T. Lesiak, E. D. Lesser, B. Leverington, A. Li, C. Li, C. Li, H. Li, J. Li, K. Li, L. Li, M. Li, P. Li, P. -R. Li, Q. Li, T. Li, T. Li, Y. Li, Y. Li, Y. Li, Z. Lian, Q. Liang, X. Liang, Z. Liang, S. Libralon, A. Lightbody, C. Lin, T. Lin, R. Lindner, H. Linton, R. Litvinov, D. Liu, F. L. Liu, G. Liu, K. Liu, S. Liu, W. Liu, Y. Liu, Y. Liu, Y. L. Liu, G. Loachamin Ordonez, I. Lobo, A. Lobo Salvia, A. Loi, T. Long, F. C. L. Lopes, J. H. Lopes, A. Lopez Huertas, C. Lopez Iribarnegaray, S. López Soliño, Q. Lu, C. Lucarelli, D. Lucchesi, M. Lucio Martinez, Y. Luo, A. Lupato, E. Luppi, K. Lynch, S. Lyu, X. -R. Lyu, G. M. Ma, H. Ma, S. Maccolini, F. Machefert, F. Maciuc, B. Mack, I. Mackay, L. M. Mackey, L. R. Madhan Mohan, M. J. Madurai, D. Magdalinski, D. Maisuzenko, J. J. Malczewski, S. Malde, L. Malentacca, A. Malinin, T. Maltsev, G. Manca, G. Mancinelli, C. Mancuso, R. Manera Escalero, F. M. Manganella, D. Manuzzi, D. Marangotto, J. F. Marchand, R. Marchevski, U. Marconi, E. Mariani, S. Mariani, C. Marin Benito, J. Marks, A. M. Marshall, L. Martel, G. Martelli, G. Martellotti, L. Martinazzoli, M. Martinelli, D. Martinez Gomez, D. Martinez Santos, F. Martinez Vidal, A. Martorell i Granollers, A. Massafferri, R. Matev, A. Mathad, V. Matiunin, C. Matteuzzi, K. R. Mattioli, A. Mauri, E. Maurice, J. Mauricio, P. Mayencourt, J. Mazorra de Cos, M. Mazurek, M. McCann, N. T. McHugh, A. McNab, R. McNulty, B. Meadows, S. E. R. Medaer, G. Meier, D. Melnychuk, D. Mendoza Granada, P. Menendez Valdes Perez, F. M. Meng, M. Merk, A. Merli, L. Meyer Garcia, D. Miao, H. Miao, M. Mikhasenko, D. A. Milanes, A. Minotti, E. Minucci, T. Miralles, B. Mitreska, D. S. Mitzel, R. Mocanu, A. Modak, L. Moeser, R. D. Moise, E. F. Molina Cardenas, T. Mombächer, M. Monk, S. Monteil, A. Morcillo Gomez, G. Morello, M. J. Morello, M. P. Morgenthaler, A. Moro, J. Moron, W. Morren, A. B. Morris, A. G. Morris, R. Mountain, Z. Mu, E. Muhammad, F. Muheim, M. Mulder, K. Müller, F. Muñoz-Rojas, R. Murta, V. Mytrochenko, P. Naik, T. Nakada, R. Nandakumar, T. Nanut, I. Nasteva, M. Needham, E. Nekrasova, N. Neri, S. Neubert, N. Neufeld, P. Neustroev, J. Nicolini, D. Nicotra, E. M. Niel, N. Nikitin, L. Nisi, Q. Niu, P. Nogarolli, P. Nogga, C. Normand, J. Novoa Fernandez, G. Nowak, C. Nunez, H. N. Nur, A. Oblakowska-Mucha, V. Obraztsov, T. Oeser, A. Okhotnikov, O. Okhrimenko, R. Oldeman, F. Oliva, E. Olivart Pino, M. Olocco, R. H. O'Neil, J. S. Ordonez Soto, D. Osthues, J. M. Otalora Goicochea, P. Owen, A. Oyanguren, O. Ozcelik, F. Paciolla, A. Padee, K. O. Padeken, B. Pagare, T. Pajero, A. Palano, L. Palini, M. Palutan, C. Pan, X. Pan, S. Panebianco, S. Paniskaki, G. Panshin, L. Paolucci, A. Papanestis, M. Pappagallo, L. L. Pappalardo, C. Pappenheimer, C. Parkes, D. Parmar, G. Passaleva, D. Passaro, A. Pastore, M. Patel, J. Patoc, C. Patrignani, A. Paul, C. J. Pawley, A. Pellegrino, J. Peng, X. Peng, M. Pepe Altarelli, S. Perazzini, D. Pereima, H. Pereira Da Costa, M. Pereira Martinez, A. Pereiro Castro, C. Perez, P. Perret, A. Perrevoort, A. Perro, M. J. Peters, K. Petridis, A. Petrolini, S. Pezzulo, J. P. Pfaller, H. Pham, L. Pica, M. Piccini, L. Piccolo, B. Pietrzyk, G. Pietrzyk, R. N. Pilato, D. Pinci, F. Pisani, M. Pizzichemi, V. M. Placinta, M. Plo Casasus, T. Poeschl, F. Polci, M. Poli Lener, A. Poluektov, N. Polukhina, I. Polyakov, E. Polycarpo, S. Ponce, D. Popov, K. Popp, S. Poslavskii, K. Prasanth, C. Prouve, D. Provenzano, V. Pugatch, A. Puicercus Gomez, G. Punzi, J. R. Pybus, Q. 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Original paper licensed under CC BY 4.0 (http://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine the universe as a giant, high-speed racetrack where tiny particles zoom around at nearly the speed of light. At the LHCb experiment, scientists are like super-sleuths watching a very specific, rare crash: a heavy particle called a B0 meson breaking apart into a lighter K*0 meson and a pair of muons (which are like heavy, ghostly cousins of electrons).

This isn't just any crash. In the Standard Model—the rulebook physicists use to describe how the universe works—this specific breakup should happen in a very predictable way, like a clockwork toy. But for a while, the clock has been ticking slightly out of sync with the rulebook.

The Big Reveal: A More Precise Look

In this new study, the LHCb team used a massive amount of data (equivalent to 8.4 fb⁻¹ of proton-proton collisions collected between 2011 and 2018) to take the most detailed look yet at this decay. Think of it as upgrading from a blurry security camera to a 4K, slow-motion camera that can see every tiny twist and turn of the particles.

What they found:
The team measured a whole bunch of "angular observables." Imagine the particles flying out like shrapnel from a firework. These observables tell us exactly which direction the pieces fly and how they spin.

The Good News: The "CP asymmetry" observables (which check if the universe treats matter and antimatter differently in this crash) are all consistent with zero. In other words, the universe is playing fair here; no sneaky differences between matter and antimatter were found.
The Tension: When they looked at the "CP-averaged" observables (the average behavior of the particles), the results still show a pattern of tensions with the Standard Model predictions. Specifically, in certain energy ranges (like 4.0 < q² < 6.0 GeV²/c⁴), the data disagrees with the rulebook by about 2.6 to 2.7 standard deviations (σ).

New Tools in the Detective's Kit

This paper isn't just a re-run of old experiments; it brings some brand-new tricks to the table:

The "S-Wave" Mystery: Previously, scientists mostly looked at the main "P-wave" spin of the particles. This study is the first to fully measure the "S-wave" contribution (a different way the particles can spin) and how it interferes with the main spin. It's like finally hearing the background hum in a song, not just the main melody.
Heavy Muons Matter: The team realized that the mass of the muons themselves actually changes the math, especially at lower energy levels (below 6 GeV²/c⁴). For the first time, they accounted for this "heaviness" in their calculations, which turned out to be important.
Narrower Bins: Instead of looking at the data in broad, fuzzy buckets, they sliced the energy ranges into much narrower strips. This gave them a sharper picture of exactly where the tension with the Standard Model happens.

What They Ruled Out (and What They Didn't)

The team was very careful to check if the "glitches" they saw were just because they didn't understand the background noise.

They ruled out the idea that the tension is caused by simple, long-distance effects (like the particles interacting in a way we already know how to calculate). Their analysis suggests these effects are not large enough to explain the discrepancy.
They did NOT rule out the possibility of "New Physics." In fact, the tension suggests that something new might be contributing to the decay. If you imagine the Standard Model as a recipe, the data suggests there might be an extra, secret ingredient (like a new particle or force) that the recipe doesn't list yet.
They did NOT prove that New Physics exists. A tension of 2.7σ is like seeing a shadow that looks a bit like a monster; it's suspicious, but it's not a confirmed monster sighting (which usually requires 5σ). The paper explicitly states that the results "continue to exhibit the pattern of tensions," meaning the mystery remains unsolved.

The Bottom Line

The authors measured the decay of the B0 → K*0µ+µ− particle with unprecedented precision. They found that while the universe treats matter and antimatter equally in this process, the way the particles fly and spin still doesn't quite match the Standard Model's predictions in specific energy zones.

They calculated that the data fits a theory where a specific parameter (called Re(C9)) is shifted by about -0.93 from the Standard Model value. This shift is significant (about 4.1σ when combining all data), but it's still a "suggestion" of new physics, not a confirmed discovery. The paper ends by saying the tension is real and intriguing, but the case is still open, waiting for more data to see if the "ghost" in the machine is actually a new particle or just a trick of the light.

Technical Summary of CERN-EP-2025-278: Comprehensive analysis of the $B^0 \to K^{*0}\mu^+\mu^-$ decay

Problem and Context
Experimental measurements of the rare flavor-changing neutral current decay $B^0 \to K^{*0}\mu^+\mu^-$ (where $K^{*0} \to K^+\pi^-$ ) have exhibited persistent discrepancies with Standard Model (SM) predictions. These processes, mediated by the underlying $b \to s\mu^+\mu^-$ quark transition, are highly suppressed in the SM, occurring only via virtual quantum loops. This suppression makes them sensitive probes for New Physics (NP), potentially manifesting as deviations in Wilson coefficients such as $C_9$ . However, the interpretation of these tensions remains debated, with ongoing discussions regarding whether they stem from NP or underestimated SM long-distance effects. Previous analyses have largely treated the $K^+\pi^-$ system as a pure $P$ -wave resonance ( $K^*(892)^0$ ) and often neglected lepton mass effects or the interference with the $S$ -wave component.

Methodology
This analysis utilizes proton-proton collision data collected by the LHCb experiment corresponding to an integrated luminosity of 8.4 fb $^{-1}$ (covering 2011, 2012, and 2016–2018). The study employs a five-dimensional unbinned maximum-likelihood fit to the differential decay rate as a function of the dimuon invariant mass squared ( $q^2$ ), the $K^+\pi^-$ invariant mass ( $m(K^+\pi^-)$ ), and the three decay angles ( $\theta_\ell, \theta_K, \phi$ ).

Key methodological innovations and features include:

Simultaneous Treatment of Kinematics: For the first time, the analysis simultaneously treats all relevant kinematic variables, explicitly incorporating $m(K^+\pi^-)$ over a wider range ( $0.7459 < m(K^+\pi^-) < 1.0959$ GeV/ $c^2$ ) than previous studies. This allows for the direct measurement of interference between $P$ -wave ( $K^*$ ) and $S$ -wave contributions.
Lepton Mass Effects: The analysis accounts for the finite mass of the muon, which is found to have a significant impact on angular observables for $q^2 \lesssim 6$ GeV $^2/c^4$ . Three fitting models are employed: "fully massive" (no assumptions), "partially massive" (massless lepton relations applied where valid), and "massless."
CP Asymmetries: The study extracts the full set of CP-averaged angular observables ( $S_i$ ) and CP-asymmetry observables ( $A_i$ ) in a single simultaneous fit across six subsamples (divided by $B^0/\bar{B}^0$ and run periods).
Background Suppression: A dedicated Boosted Decision Tree (BDT) classifier is used to suppress combinatorial backgrounds. Peaking backgrounds from misidentified particles (e.g., $B_s^0 \to \phi\mu^+\mu^-$ , $B^0 \to J/\psi K^{*0}$ ) are reduced via kinematic vetoes and neural network classifiers.
Validation: The analysis was performed twice using two independently developed frameworks to validate results. Systematic uncertainties are evaluated coherently across all $q^2$ bins, and the full covariance matrix of observables is provided.

Key Contributions
This paper presents several "firsts" in the analysis of this decay mode:

Full S-wave and Interference Observables: It reports the complete set of observables pertaining to the $K^+\pi^-$ $S$ -wave contribution and the interference between $P$ - and $S$ -waves.
Lepton Mass Treatment: It is the first analysis to account for muon mass effects when determining angular observables.
Differential Branching Fraction: It simultaneously measures the differential branching fraction relative to the normalization mode $B^0 \to J/\psi(\to \mu^+\mu^-)K^+\pi^-$ without relying on a specific model of the angular distribution.
Complete CP Asymmetry Set: It provides the first measurement of the full set of CP-asymmetry observables alongside the CP-averaged ones.
Refined Binning: It utilizes narrower $q^2$ bins compared to previous analyses to improve the understanding of $q^2$ dependence.

Results

CP Asymmetries: All extracted CP-asymmetry observables are consistent with zero, showing no significant deviation from SM expectations.
CP-Averaged Observables: The measurements of CP-averaged observables ( $S_i$ $S_{i}$ ) and the differential branching fraction continue to exhibit the pattern of tensions with SM predictions observed in previous analyses using subsets of this dataset.
- The optimized observable $P'_5$ shows discrepancies with SM predictions (specifically the GRvDV and ABCDMN scenarios) in the $1.1 < q^2 < 2.5$ , $4.0 < q^2 < 6.0$ , and $6.0 < q^2 < 8.0$ GeV $^2/c^4$ bins, with tensions ranging from 1.6 $\sigma$ to 2.7 $\sigma$ .
- The forward-backward asymmetry ( $A_{FB}$ ) shows tensions of 1.7 $\sigma$ to 2.5 $\sigma$ in the $2.5 < q^2 < 6.0$ GeV $^2/c^4$ region.
- The differential branching fraction is 1.5 $\sigma$ to 2.1 $\sigma$ below SM predictions in the $1.1 < q^2 < 6.0$ GeV $^2/c^4$ bin.
Global Fits: When fitting the results to the SM using the Flavio and EOS packages, the discrepancy with the SM value of the real part of the Wilson coefficient $C_9$ ( $\text{Re}(C_9)$ ) increases to 3.6 $\sigma$ (Flavio) and 3.8 $\sigma$ (EOS). Including the differential branching fraction raises this significance to 4.1 $\sigma$ (Flavio) and 4.0 $\sigma$ (EOS). The best fit suggests a shift in $\text{Re}(C_9)$ of approximately $-0.94$.

Significance
The paper claims that this analysis provides the most precise measurements to date of the CP-averaged angular observables, associated CP asymmetries, and the differential branching fraction for the $B^0 \to K^{*0}\mu^+\mu^-$ decay. By including the $S$ -wave contribution, accounting for lepton masses, and measuring the full set of CP asymmetries, the analysis offers a more complete and robust test of the Standard Model. The results reinforce the existence of tensions with SM predictions in the $b \to s\mu^+\mu^-$ sector, particularly in the $P'_5$ observable and the branching fraction, while confirming that CP violation is consistent with zero. The provision of the full covariance matrix and the model-independent determination of branching fractions are intended to facilitate subsequent phenomenological analyses and global fits to New Physics models.

The Big Reveal: A More Precise Look

New Tools in the Detective's Kit

What They Ruled Out (and What They Didn't)

The Bottom Line

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