Search

The field of particle physics is at the crossroads. The discovery of a Higgs-like boson completed the Standard Model (SM), but the lacking observation of convincing resonances Beyond the SM (BSM) offers no guidance for the future of particle physics. On the other hand, the motivation for New Physics has not diminished and is, in fact, reinforced by several striking anomalous results in many experiments. Here we summarise the status of the most significant anomalies, including the most recent results for the flavour anomalies, the multi-lepton anomalies at the LHC, the Higgs-like excess at around 96 GeV, and anomalies in neutrino physics, astrophysics, cosmology, and cosmic rays. While the LHC promises up to 4 ab - 1 of integrated luminosity and far-reaching physics programmes to unveil BSM physics, we consider the possibility that the latter could be tested with present data, but that systemic shortcomings of the experiments and their search strategies may preclude their discovery for several reasons, including: final states consisting in soft particles only, associated production processes, QCD-like final states, close-by SM resonances, and SUSY scenarios where no missing energy is produced. New search strategies could help to unveil the hidden BSM signatures, devised by making use of the CERN open data as a new testing ground. We discuss the CERN open data with its policies, challenges, and potential usefulness for the community. We showcase the example of the CMS collaboration, which is the only collaboration regularly releasing some of its data. We find it important to stress that individuals using public data for their own research does not imply competition with experimental efforts, but rather provides unique opportunities to give guidance for further BSM searches by the collaborations. Wide access to open data is paramount to fully exploit the LHCs potential., The European Physical Journal C, 82 (8), ISSN:1434-6044, ISSN:1434-6052

Journal of high energy physics 2021(1), 194 (2021). doi:10.1007/JHEP01(2021)194, Models incorporating flavoured dark matter provide an elegant solution to the dark matter problem, evading the tight LHC and direct direction constraints on simple WIMP models. In Dark Minimal Flavour Violation, a simple framework of flavoured dark matter with new sources of flavour violation, the constraints from thermal freeze-out, direct detection experiments, and flavour physics create well-defined benchmark scenarios for these models. We study the LHC phenomenology of four such scenarios, focusing on final states where a single top quark is produced accompanied by no jets, one jet from the fragmentation of light quarks or a $b$-tagged jet. For each of these signatures we develop a realistic LHC analysis, and we show that the proposed analyses would increase the parameter space coverage for the four benchmarks, compared to existing flavour-conserving LHC analyses. Finally we show the projected discovery potential of the considered signatures for the full LHC statistics at 14 TeV, and for the High Luminosity LHC., Published by SISSA, [Trieste]

We explore signals of new physics with two Higgs bosons and large missing transverse energy at the LHC. Such a signature is characteristic of models for dark matter or other secluded particles that couple to the standard model through an extended scalar sector. Our goal is to provide search strategies and an interpretation framework for this new signature that are applicable to a large class of models. To this end, we define simplified models of hidden sectors leading to two different event topologies: symmetric decay, i.e., pair-produced mediators decaying each into a Higgs plus invisible final state; and di-Higgs resonance, i.e., resonant Higgs-pair production recoiling against a pair of invisible particles. For both scenarios, we optimize the discovery potential by performing a multi-variate analysis of final states with four bottom quarks and missing energy, employing state-of-the-art machine learning algorithms for signal-background discrimination. We determine the parameter space that the LHC can test in both scenarios, thus facilitating an interpretation of our results in terms of complete models. Di-Higgs production with missing energy is competitive with other missing energy searches and thus provides a new opportunity to find hidden particles at the LHC., 20 pages, 11 figures, 1 table. v2: clarifying comments and few references added, matches published version

These proceedings review the status of New Physics contributions to flavour violating $B$ decays. The anomalies in charged and neutral current $B$ decays related to lepton flavour universality violation have received a substantial amount of attention over the past years, and we discuss the current status in light of the new data presented earlier this year. We also recall a tension in the neutral $B$ meson mixing observables $\Delta M_d$ and $\Delta M_s$ and in particular their ratio, when compared with their SM predictions obtained using tree-level determinations of the CKM matrix and the recent lattice QCD results for the relevant hadronic matrix elements. Last but not least, we advocate kaon physics as a unique probe of very high energy scales and briefly discuss the current status of $\varepsilon'/\varepsilon$ and $K\to\pi\nu\bar\nu$., Comment: 15 pages, 4 figures. v2: typos corrected and reference added. Proceedings of the XXIX International Symposium on Lepton Photon Interactions at High Energies - LeptonPhoton2019, 5-10 August 2019, Toronto, Canada

We investigate the phenomenology of a simplified model of flavoured Dark Matter (DM), with a dark fermionic flavour triplet coupling to the left-handed $SU(2)_L$ quark doublets via a scalar mediator. The DM-quark coupling matrix is assumed to constitute the only new source of flavour and CP violation, following the hypothesis of Dark Minimal Flavour Violation. We analyse the constraints from LHC searches, from meson mixing data in the $K$, $D$, and $B_{d,s}$ meson systems, from thermal DM freeze-out, and from direct detection experiments. Our combined analysis shows that while the experimental constraints are similar to the DMFV models with DM coupling to right-handed quarks, the multitude of couplings between DM and the SM quark sector resulting from the $SU(2)_L$ structure implies a richer phenomenology and significantly alters the resulting impact on the viable parameter space., 23 pages, 11 figures. v2: some clarifying comments and references added, matches published version

We study a simplified model of top-flavoured dark matter in the framework of Dark Minimal Flavour Violation. In this setup the coupling of the dark matter flavour triplet to right-handed up-type quarks constitutes the only new source of flavour and CP violation. The parameter space of the model is restricted by LHC searches with missing energy final states, by neutral $D$ meson mixing data, by the observed dark matter relic abundance, and by the absence of signal in direct detection experiments. We consider all of these constraints in turn, studying their implications for the allowed parameter space. Imposing the mass limits and coupling benchmarks from collider searches, we then conduct a combined analysis of all the other constraints, revealing their non-trivial interplay. Especially interesting is the combination of direct detection and relic abundance constraints, having a severe impact on the structure of the dark matter coupling matrix. We point out that future bounds from upcoming direct detection experiments, such as XENON1T, XENONnT, LUX-ZEPLIN, and DARWIN, will exclude a large part of the parameter space and push the DM mass to higher values., Comment: 34 pages, 23 figures. v2: clarifying comments and few references added, matches published version

Precise lattice QCD results for hadronic matrix elements, decay constants and form factors play a crucial role in the determination of CKM matrix elements and in the identification of possible new physics contributions to flavour violating observables. This article reviews the implications of recent lattice QCD results on the phenomenology of flavour and CP violating meson decays, and highlights some future directions for lattice QCD calculations which would have a major impact on flavour phenomenology., 17 pages, 7 figures. Plenary talk given at The 34th International Symposium on Lattice Field Theory (Lattice 2016), Southampton, July 2016

We study constraints from LHC run I on squark and gluino masses in the presence of squark flavor violation. Inspired by the concept of `flavored naturalness', we focus on the impact of a non-zero stop-scharm mixing and mass splitting in the right-handed sector. To this end, we recast four searches of the ATLAS and CMS collaborations, dedicated either to third generation squarks, to gluino and squarks of the first two generations, or to charm-squarks. In the absence of extra structure, the mass of the gluino provides an additional source of fine tuning and is therefore important to consider within models of flavored naturalness that allow for relatively light squark states. When combining the searches, the resulting constraints in the plane of the lightest squark and gluino masses are rather stable with respect to the presence of flavor-violation, and do not allow for gluino masses of less than 1.2 TeV and squarks lighter than about 550 GeV. While these constraints are stringent, interesting models with sizable stop-scharm mixing and a relatively light squark state are still viable and could be observed in the near future., 34 pages. v2: clarifying comments and few references added, typos fixed, matches published version

The Littlest Higgs Model with T-parity (LHT) belongs to the simplest new physics scenarios with new sources of flavour and CP violation. We present a new analysis of quark observables in the LHT model in view of the oncoming flavour precision era. We use all available information on the CKM parameters, lattice QCD input and experimental data on quark flavour observables and corresponding theoretical calculations, taking into account new lower bounds on the symmetry breaking scale and the mirror quark masses from the LHC. We investigate by how much the branching ratios for a number of rare $K$ and $B$ decays are still allowed to depart from their SM values. This includes $K^+\to\pi^+\nu\bar\nu$, $K_L\to\pi^0\nu\bar\nu$, $K_L\to \mu^+\mu^-$, $\epsilon'/\epsilon$, $B\to X_s\gamma$, $B_{s,d}\to\mu^+\mu^-$, $B\to K^{(*)}\ell^+\ell^-$, $B\to K^{(*)}\nu\bar\nu$. Taking into account the constraints from $\Delta F=2$ processes, significant departures from the SM predictions for $K^+\to\pi^+\nu\bar\nu$ and $K_L\to\pi^0\nu\bar\nu$ are possible while the effects in $B$ decays are much smaller. In particular, the LHT model favours $\mathcal{B}(B_{s}\to\mu^+\mu^-) \ge \mathcal{B}(B_{s}\to\mu^+\mu^-)_{\rm SM}$, which is not supported by the data, and the present anomalies in $B\to K^{(*)}\ell^+\ell^-$ decays cannot be explained in this model. With the recent lattice and large $N$ input the imposition of the $\epsilon'/\epsilon$ constraint implies a significant suppression of the branching ratio for $K_L\to\pi^0\nu\bar\nu$ with respect to its SM value while allowing only for small modifications for $K^+\to\pi^+\nu\bar\nu$. Finally, we investigate how the LHT physics could be distinguished from other models by means of indirect measurements and discuss the consequences for quark flavour observables of not finding any LHT state in the coming years., Comment: 36 pages, 12 figures. v2: clarifying comments added, matches published version

We show that a large mixing between the right-handed charm and top squarks (i) is allowed by low-energy flavour constraints; (ii) reduces the experimental bound on the stop mass; (iii) has a mild, but beneficial, effect on fine-tuning; (iv) leads to interesting signatures at the LHC not presently investigated by experiments. We estimate the current bound on the stop mass, in presence of flavour mixing, and discuss the new collider signatures. The signal in the t anti-c (c anti-t) + missing E_T channel is large enough that it can be immediately searched for experimentally, while the signature with same-sign tops and missing E_T requires a luminosity upgrade of the LHC., 20 pages, 12 figures - clarifying comments added, version to be published in JHEP

I provide an overview of the connections between flavor violating observables in the K and B meson systems beyond the Standard Model (BSM). Model independent correlations, both in and beyond the MFV framework, as well as results obtained in specific models are discussed., 5 pages, 7 figures. Proceedings for CIPANP 2012 - Eleventh Conference on the Intersections of Particle and Nuclear Physics, St.Petersburg FL, May 29 - June 3 2012

Three body decays can exhibit CP violation that arises from interfering diagrams with different orderings of the final state particles. We construct several momentum asymmetry observables that are accessible in a hadron collider environment where some of the final state particles are not reconstructed and not all the kinematic information can be extracted. We discuss the complications that arise from the different possible production mechanisms of the decaying particle. Examples involving heavy neutralino decays in supersymmetric theories and heavy Majorana neutrino decays in Type-I seesaw models are examined., 20 pages, 9 figures. Clarifying comments and one reference added, matches published version

This report provides a succinct summary of the physics programme of SuperB, and describes that potential in the context of experiments making measurements in flavour physics over the next 10 to 20 years. Detailed comparisons are made with Belle II and LHCb, the other B physics experiments that will run in this decade. SuperB will play a crucial role in defining the landscape of flavour physics over the next 20 years., Comment: 20 pages, 6 figures

We present the electroweak and flavour structure of a model with a warped extra dimension and the bulk gauge group SU(3) x SU(2)_L x SU(2)_R x P_LR x U(1)_X. The presence of SU(2)_R implies an unbroken custodial symmetry in the Higgs system allowing to eliminate large contributions to the T parameter, whereas the P_LR symmetry and the enlarged fermion representations provide a custodial symmetry for flavour diagonal and flavour changing couplings of the SM Z boson to left-handed down-type quarks. We diagonalise analytically the mass matrices of charged and neutral gauge bosons including the first KK modes. We present the mass matrices for quarks including heavy KK modes and discuss the neutral and charged currents involving light and heavy fields. We give the corresponding complete set of Feynman rules in the unitary gauge., 74 pages, 2 figures. clarifying comments and references added, version to be published in JHEP

With the advent of the LHC, we will be able to probe New Physics (NP) up to energy scales almost one order of magnitude larger than it has been possible with present accelerator facilities. While direct detection of new particles will be the main avenue to establish the presence of NP at the LHC, indirect searches will provide precious complementary information, since most probably it will not be possible to measure the full spectrum of new particles and their couplings through direct production. In particular, precision measurements and computations in the realm of flavour physics are expected to play a key role in constraining the unknown parameters of the Lagrangian of any NP model emerging from direct searches at the LHC. The aim of Working Group 2 was twofold: on one hand, to provide a coherent, up-to-date picture of the status of flavour physics before the start of the LHC; on the other hand, to initiate activities on the path towards integrating information on NP from high-pT and flavour data., Comment: Report of Working Group 2 of the CERN Workshop ``Flavour in the era of the LHC'', Geneva, Switzerland, November 2005 -- March 2007

We demonstrate that in the class of models with Constrained Minimal Flavour Violation (CMFV), in which the CKM matrix is the only source of CP violation and B^0_q-\bar B^0_q mixings (q=d,s) are described by a single operator (\bar b q)_{V-A} (\bar b q)_{V-A}, the lower bounds on the mass differences Delta M_{s,d} are simply given by their Standard Model values (Delta M_{s,d})_SM with two possible exceptions that we identify. Our proof involves all possible charged gauge boson, Goldstone boson and physical charged and neutral scalar exchanges and assumes that the masses of new charge +2/3 singlet heavy fermions T_i that mix with the top quark have all to be larger than m_t, which is chosen by nature. Similarly, the additional charged gauge bosons have to satisfy M_i>M_W, while no such bound needs to be set on the charged and neutral scalar masses. The two possible exceptions arise in the presence of U(1) neutral gauge bosons and Majorana fermions in box diagrams with flavour violating couplings. However in the case of the MSSM with CMFV and low tan beta our bound is satisfied in spite of gluino and neutralino contributions., 18 pages, 4 figures. v2: Discussion of neutral particle contributions added, conclusions unchanged. v3: Discussion of Majorana fermion contributions improved, conclusions unchanged

Motivated by the recently improved results from the Fermilab Lattice and MILC Collaborations on the hadronic matrix elements entering $\Delta M_{s,d}$ in $B_{s,d}^0-\bar B_{s,d}^0$ mixing, we determine the Universal Unitarity Triangle (UUT) in models with Constrained Minimal Flavour Violation (CMFV). Of particular importance are the very precise determinations of the ratio $|V_{ub}|/|V_{cb}|=0.0864\pm0.0025$ and of the angle $\gamma=(63.0\pm 2.1)^\circ$. They follow in this framework from the experimental values of $\Delta M_{d}/\Delta M_s$ and of the CP-asymmetry $S_{\psi K_S}$. As in CMFV models the new contributions to meson mixings can be described by a single flavour-universal variable $S(v)$, we next determine the CKM matrix elements $|V_{ts}|$, $|V_{td}|$, $|V_{cb}|$ and $|V_{ub}|$ as functions of $S(v)$ using the experimental value of $\Delta M_s$ as input. The lower bound on $S(v)$ in these models, derived by us in 2006, implies then upper bounds on these four CKM elements and on the CP-violating parameter $\varepsilon_K$, which turns out to be significantly below its experimental value. This strategy avoids the use of tree-level determinations of $|V_{ub}|$ and $|V_{cb}|$ that are presently subject to considerable uncertainties. On the other hand if $\varepsilon_K$ is used instead of $\Delta M_s$ as input, $\Delta M_{s,d}$ are found significantly above the data. In this manner we point out that the new lattice data have significantly sharpened the tension between $\Delta M_{s,d}$ and $\varepsilon_K$ within the CMFV framework. This implies the presence of new physics contributions beyond this framework that are responsible for the breakdown of the flavour universality of the function $S(v)$. We also present the implications of these results for $K^+\to\pi^+\nu\bar\nu$, $K_L\to\pi^0\nu\bar\nu$ and $B_{s,d}\to\mu^+\mu^-$ within the Standard Model.