A search for new physics in central exclusive production using the missing mass technique with the CMS detector and the CMS-TOTEM precision proton spectrometer
A generic search is presented for the associated production of a Z boson or a photon with an additional unspecified massive particle X, pp $\to$ pp + Z/$γ$ + X, in proton-tagged events from proton-proton collisions at $\sqrt{s}$ = 13 TeV, recorded in 2017 with the CMS detector and the CMS-TOTEM precision proton spectrometer. The missing mass spectrum is analysed in the 600-1600 GeV range and a fit is performed to search for possible deviations from the background expectation. No significant excess in data with respect to the background predictions has been observed. Model-independent upper limits on the visible production cross section of pp $\to$ pp + Z/$γ$ + X are set.
Exclusive and diffractive physics measurements are important for the better understanding of the non-perturbative regime of QCD. Two recent results of the CMS experiment is presented in this paper. The total and differential cross sections of central exclusive $π^+π^-$ production are measured at 5.02 and 13 TeV in the $p_{\mathrm{T}}(π) > 0.2~$GeV/$c$ and $|η(π)| < 2.4$ kinematic region. The invariant mass distribution is fitted by the sum of a continuum and four interfering relativistic Breit-Wigner functions. In the second part of the paper the measurement of the single diffractive dijets is…
The CMS+TOTEM Precision Proton Spectrometer operated for the first time in 2016, collecting data during $pp$ collisions at $\sqrt{s} = 13$ TeV at the CERN Large Hadron Collider. Procedures for the detector alignment, optics corrections, and background estimations were developed, and applied to an analysis of the process $pp \rightarrow p μ^{+}μ^{-} p^{(*)}$ with dimuon masses larger than 110 GeV. A total of 12 candidate events are observed, corresponding to an excess of $>4σ$ over the background prediction. This constitutes the first evidence for this process at such masses, and demonstrates t…
A search for central exclusive production of top quark pairs ($\mathrm{t}\bar{\mathrm{t}}$) is presented using collision data collected by CMS and the CMS-TOTEM Precision Proton Spectrometer in 2017. A data-driven method to estimate the background from coincidences of inclusive events and pileup protons is described, as well as the development of a Boosted Decision Tree classifier to separate the exclusive $\mathrm{t}\bar{\mathrm{t}}$ signal from the inclusive $\mathrm{t}\bar{\mathrm{t}}$ background. The first-ever upper limits on the cross section of exclusive $\mathrm{t}\bar{\mathrm{t}}$ are…
The TOTEM experiment with its detectors in the forward region of CMS and the Roman Pots along the beam line will determine the total pp cross-section via the optical theorem by measuring both the elastic cross-section and the total inelastic rate. TOTEM will have dedicated runs with special high-beta* beam optics and a reduced number of proton bunches resulting in a low effective luminosity between 1.6 x 10^{28} cm^{-2} s^{-1} and 2.4 x 10^{29} cm^{-2} s^{-1}. In these special conditions also an absolute luminosity measurement will be made, allowing the calibration of the CMS luminosity monito…
Pseudorapidity (eta) distributions of charged particles produced in proton-proton collisions at a centre-of-mass energy of 8 TeV are measured in the ranges abs(eta) < 2.2 and 5.3 < abs(eta) < 6.4 covered by the CMS and TOTEM detectors, respectively. The data correspond to an integrated luminosity of 45 inverse microbarns. Measurements are presented for three event categories. The most inclusive category is sensitive to 91-96% of the total inelastic proton-proton cross section. The other two categories are disjoint subsets of the inclusive sample that are either enhanced or depleted in single d…
We describe the most recent results from the Proton Precision Spectrometer from the CMS and TOTEM collaborations, namely the first observation of exclusive di-lepton production at high mass at the LHC, and the prospects concerning the sensitivity to quartic anomalous couplings..
Recent CMS results on diffraction are presented. These include the measurements of the soft diffractive cross sections, of the forward rapidity gap cross section, of the diffractive dijet cross section, the measurement of a large rapidity gap in W and Z boson events and the measurement of the pseudorapidity distribution of charged particles in a single diffractive enhanced sample. This last measurement is the first common result of the CMS and TOTEM collaborations. Some prospects of common CMS-TOTEM data taking are also discussed.
The process pp$\to\ell^+\ell^-$p$^{(*)}$, with $\ell^+\ell^-$ a muon or an electron pair produced at midrapidity with mass larger than 110 GeV, has been observed for the first time at the LHC in pp collisions at $\sqrt{s} =$ 13 TeV. One of the two scattered protons is measured in the CMS-TOTEM precision proton spectrometer (CT-PPS), which operated for the first time in 2016. The second proton either remains intact or is excited and then dissociates into a low-mass state p$^{*}$, which is undetected. The measurement is based on an integrated luminosity of 9.4 fb$^{-1}$ collected during standard…
At the LHC, diffractive physics will be explored by the dedicated experiment TOTEM whose Technical Design Report has been approved in Summer 2004. The experimental programme will be carried out partly in TOTEM standalone mode for purely forward phenomena like elastic scattering, and partly in collaboration with CMS for processes requiring a full rapidity coverage. ATLAS and ALICE are interested in diffraction for a later stage. This article presents the TOTEM/CMS running scenario for diffractive physics in the first year of LHC. We discuss which processes are within reach and with which statis…
We analyze the problem of correlating pp interaction data from the central detectors with a subevent measured in an independent system of leading proton detectors using FP420 as an example. FP420 is an R&D project conducted by a collaboration formed by members of ATLAS and CMS to investigate the possibility of detecting new physics in the central exclusive channel, PP -> P + X + P,where the central system X may be a single particle, for example a Standard Model Higgs boson. With standard LHC optics, the protons emerge from the beam at a distance of 420m from the Interaction Point, for M_X ~ 12…
Measurements are presented of the single-diffractive dijet cross section and the diffractive cross section as a function of the proton fractional momentum loss $ξ$ and the four-momentum transfer squared $t$. Both processes pp$\to$pX and pp$\to$Xp, ie with the proton scattering to either side of the interaction point, are measured, where X includes at least two jets; the results of the two processes are averaged. The analyses are based on data collected simultaneously with the CMS and TOTEM detectors at the LHC in proton-proton collisions at $\sqrt{s}$= 8 TeV during a dedicated run with $β^{\as…
The CMS/TOTEM and ATLAS collaborations carry out a program of forward physics with several near-beam detectors extending their coverage to high pseudorapidities. This instrumentation includes calorimeters (CASTOR and ZDC), tracking devices (TOTEM T1 and T2), proton taggers (Roman Pots and FP420), and instrumentation dedicated to luminosity monitoring and normalisation. A rich physics program is accessible, including soft QCD interactions, Diffraction, photon-induced physics and luminosity measurements.
In this talk we present a selection of forward physics results recently obtained with the run-1 and run-2 LHC data by the CMS, LHCf and TOTEM experiments. The status of the very forward LHC proton spectrometer, CT-PPS, is discussed: emphasis is given to the physics potential of CT-PPS and to the analyses that are currently ongoing with the data collected in 2016. Very recent forward measurements obtained with the LHCf and the CMS-CASTOR calorimeter are then addressed. In particular, CMS measured the inclusive energy spectrum in the very forward direction for proton-proton collisions at a cente…
Recent results in soft QCD at LHC by the ATLAS, CMS and TOTEM Collaborations are presented. Special focus is reserved to studies in diffractive and forward physics, and to the underlying event, with comparison with previous results and highlighting novel techniques.
We present recent results on Minimum Bias, MPI and DPS, Diffractive and Exclusive studies using data collected during Run 1 of the LHC. The measurements include data collected in pp collisions at $\sqrt s = 7$, and $8$ TeV by the CMS Collaboration. Double parton scattering is investigated in several final states including vector bosons and jets, and the effective cross section results are compared to other experiments and to MPI models tuned to recent underlying event measurements at CMS. Inclusive diffractive cross sections are discussed and compared to models, while searches and measurements…
The first physics results from the TOTEM experiment are here reported, concerning the measurements of the total, differential elastic, elastic and inelastic pp cross-section at the LHC energy of $\sqrt{s}$ = 7 TeV, obtained using the luminosity measurement from CMS. A preliminary measurement of the forward charged particle $η$ distribution is also shown.
In this report, we describe the most recent results on exclusive diffraction from the ATLAS, CMS, LHCb, TOTEM experiments at the LHC concerning exclusive pions, $J/Ψ$, $Ψ(2S)$, dilepton, diphoton, $WW$ productions and prospects concerning the search for anomalous couplings and axion-like particle production.
The TOTEM experiment at the LHC measures the total proton-proton cross section with the luminosity-independent method and the elastic proton-proton cross-section over a wide |t|-range. It also performs a comprehensive study of diffraction, spanning from cross-section measurements of individual diffractive processes to the analysis of their event topologies. Hard diffraction will be studied in collaboration with CMS taking advantage of the large common rapidity coverage for charged and neutral particle detection and the large variety of trigger possibilities even at large luminosities. TOTEM wi…
We describe recent results from CMS and TOTEM on hard diffraction, diffractive jets and jet gap jet events. We also give the first sensitivities and limits on quartic anomalous couplings and axion-like particles at high mass using the LHC as a $γγ$ collider. The predicted sensitivities with 300 fb$^{-1}$ are better by two or three orders of magnitude compared to the more standard methods at the LHC without measuring intact protons after collision
Results of exclusive photoproduction of Upsilon states in Ultraperipheral collisions (UPC) of protons and ions with the CMS experiment are presented, which provides a clean probe of the gluon distribution at small values of parton fractional momenta $x \approx 10^{-2} 10^{4}$ at central rapidities (|y| $< 2.5$). The three Upsilon states (1S, 2S, 3S) are measured in the dimuon decay channel along with the photon-photon decaying to dimuon QED continuum at $\sqrt{s_{NN}}=5.02$~TeV for integrated luminosity of $L_{int} = 35$ nb$^{-1}$. The total Upsilon photoproduction cross sections at different …
The exclusive photoproduction of $Υ$(1S), $Υ$(2S) and $Υ$(3S) mesons is studied in their leptonic ($μ^{+}μ^{-}$) decay modes, in ultraperipheral pPb collisions at $\sqrt{s_{NN}} = 5.02$ TeV. The data was recorded by the CMS experiment corresponding to an integrated luminosity of $32.6$ nb$^{-1}$. The differential cross-section for $Υ$(n) states (n=1,2,3), has been measured as a function of transverse momentum squared $p_{T}^{2}$, and rapidity $y$. The $Υ$(1S) photoproduction cross-section is extracted in the region $|y|<2.2$ as a function of the photon-proton centre-of-mass energies $W_{γp}$, …
With excellent performance the Compact Muon Solenoid (CMS) experiment has made a number of key observations in the diffractive and exclusive processes and hence in probing the Standard model in a unique way. This presentation will cover recent results on the measurement of diffractive and exclusive processes using data recorded by CMS detector at the LHC.
We report the results on the searches of exclusive production of low- and high-mass pairs with the Compact Muon Solenoid (CMS) detector in proton-proton collisions at $\sqrt{s}$ = 7 TeV. The analyses comprise the central exclusive $γγ$ production, the exclusive two-photon production of dileptons, $e^{+}e^{-}$ and $μ^{+}μ^{-}$, and the exclusive two-photon production of $W$ pairs in the asymmetric $e^{\pm}μ^{\mp}$ decay channel. No diphotons candidates are observed in data and an upper limit on the cross section is set to 1.18 pb with 95% confidence level for $E_{T}(γ)>$ 5.5 GeV and $|η(γ)|<$ 2…
Proton-proton elastic scattering has been measured by the TOTEM experiment at the CERN Large Hadron Collider at $\sqrt{s} = 7 $ TeV in special runs with the Roman Pot detectors placed as close to the outgoing beam as seven times the transverse beam size. The differential cross-section measurements are reported in the |t|-range of 0.36 to 2.5 GeV^2. Extending the range of data to low t values from 0.02 to 0.33 GeV^2,and utilizing the luminosity measurements of CMS, the total proton-proton cross section at sqrt(s) = 7 TeV is measured to be (98.3 +- 0.2(stat) +- 2.8(syst)) mb.
The feasibility studies of the central exclusive jet production at the LHC using the proton tagging technique are presented. Three classes of data taking scenarios are considered: double tag at high pile-up, single tag at low pile-up and double tag at low pile-up. Analyses were performed at the c.m. energy of 14 TeV for the ATLAS experiment, but are also valid for the CMS/TOTEM detectors.
We report the results on the search for exclusive production of $W$ pairs in the LHC with data collected by the Compact Muon Solenoid detector in proton-proton collisions at $\sqrt{s}$ = 7 TeV. The analysis comprises the two-photon production of a $W$ pairs, ${pp\to p\,W^{+}W^{-}\,p\to p\,νe^{\pm}νμ^{\mp}\,p}$. Two events are observed in data for $p_{\textrm{\footnotesize T}}(\ell)>$ 4 GeV, $|η(\ell)|<$ 2.4 and $m(μ^{\pm}e^{\mp})>$ 20 GeV, in agreement with the standard model prediction of 2.2 $\pm$ 0.4 signal events with 0.84 $\pm$ 0.15 background events. Moreover, a study of the tail of the …
Exclusive W$^{+}$W$^{-}$ pair production in photon-photon collisions during the pp runs at 7 and 8 TeV are observed and used to put constraints on the Anomalous Quartic Gauge Couplings. During the proton lead collisions in photon-induced vector meson production is observed via the decay of upsilon into two muons. The slope of the squared p$_{\rm T}$ distribution is measured to determine the size of the production region.
We present the recent measurements of exclusive processes performed in the CMS experiment at the LHC using data collected at a centre of mass energy of 7 TeV. These measurements include the double-pomeron production of photon pairs, the two-photon production of leptons pairs, and the previously undetected two-photon production of W boson pairs. While in case of the two first processes that enables to set limits on production cross-section, in the later case it provides also stringent limits on the anomalous quartic gauge couplings.
In this paper, selected CMS measurements sensitive to low-x QCD are presented: inclusive cross-sections for forward-central jets production at \sqrt{s}=7 TeV, inclusive cross-sections for forward jets production at 7 TeV and 8 TeV, inclusive to exclusive dijets production cross-sections ratios and correlations of Mueller-Navelet dijets at 7 TeV. Results for data are compared to predictions of theoretical models.
We describe the most recent results at the Large Hadron Collider from the ALICE, ATLAS, CMS, LHCb and TOTEM experiments concerning the elastic, inelastic and total cross section measurements as well as particle production in soft and hard processes.
Highlights are presented of current searches for supersymmetry produced in proton-proton collisions at the LHC, operating at sqrt(s)=7TeV. Searches with missing transverse energy are summarized from both the ATLAS and CMS experiments. A wide range of final states is covered, including recent searches with photons, leptons, and purely hadronic final states. Future developments are anticipated with extra focus on exclusive searches in electroweak and third-generation supersymmetry production.
The feasibility studies of the measurement of the central exclusive jet production at the LHC using the proton tagging technique are presented. In order to reach the low jet-mass region, single tagged events were considered. The studies were performed at the c.m. energy of 14 TeV and the ATLAS detector, but are also applicable for the CMS-TOTEM experiments. Four data-taking scenarios were considered: AFP and ALFA detectors as forward proton taggers and $β^*$ = 0.55 m and $β^*$ = 90 m optics. After the event selection, the signal-to-background ratio ranges between 5 and $10^4$. Finally, the exp…
B-hadrons are an ideal tool for advancing our current understanding of the flavor sector of the Standard Model (SM). The study of B-meson production and decays is one of the key physics themes at the Large Hadron Collider (LHC) thanks to the large production rate and the fact that B-hadrons are relatively easy to trigger on and identify due to their long lifetime and decays to muons. This talk presents the cross section measurement for the exclusive final state Bs->J/psi phi and an evaluation of the decay branching fraction from the previously published exclusive-B production cross sections. B…
Rapidity distributions are presented for events containing either a Z boson or a photon with a single jet in proton-proton collisions produced at the CERN LHC. The data, collected with the CMS detector at sqrt(s) = 7 TeV, correspond to an integrated luminosity of 5.0 inverse femtobarns. The individual rapidity distributions of the boson and the jet are consistent within 5% with expectations from perturbative QCD. However, QCD predictions for the sum and the difference in rapidities of the two final-state objects show discrepancies with CMS data. In particular, next-to-leading-order QCD calcula…
Thanks to the excellent tracking and muon identification performance, combined with a flexible trigger system, the CMS experiment at the Large Hadron Collider is conducting a rich and competitive program of measurements in the field of heavy flavor physics. We review the status of b-quark production cross section measurements in inclusive and exclusive final states, the measurement of B hadron angular correlations, the search for rare $B^0_s$ and $B^0$ decays to dimuons, and the observation of the X(3872) resonance.
Forward physics with CMS at the LHC covers a wide range of physics subjects, including very low-x QCD, underlying event and multiple interactions characteristics, gamma-mediated processes, shower development at the energy scale of primary cosmic ray interactions with the atmosphere, diffraction in the presence of a hard scale and even MSSM Higgs discovery in central exclusive production. We describe the forward detector instrumentation around the CMS interaction point and present selected feasibility studies to illustrate their physics potential.
The forward physics program of the CMS experiment at the LHC spans a broad range of diverse physics topics including studies of low-x QCD and diffractive scattering, multi-parton interactions and underlying event structure, gamma-mediated processes and luminosity determination, Monte Carlo tuning and even MSSM Higgs discovery in central exclusive production. In this article, the forward detector instrumentation around the CMS interaction point is described and the prospects for diffractive and forward physics using the CMS forward detectors are summarized. In addition, first observation of for…
Measurements of heavy flavor production in pp collisions at sqrt(s) = 7.0 TeV recorded at the CMS experiment are presented. Double differential cross sections with respect to transverse momentum and rapidity are shown for J/Psi and Upsilon(1S), Upsilon(2S), and Upsilon(3S). The inclusive open beauty rate is measured with two different techniques, including a study of the angular correlations between b jets in events with two identified b jets. Lastly, the B+, B0, and B0s production rates are measured from the reconstruction of exclusive final states.
Small-angle detectors at the LHC give access to a broad physics programme within and beyond the Standard Model (SM). We review the capabilities of ALICE, ATLAS, CMS, LHCb, LHCf and TOTEM for forward physics studies in various sectors: soft and hard diffractive processes, exclusive Higgs production, low-x QCD, ultra-high-energy cosmic-rays, and electro-weak measurements.
This paper describes the design and the performance of the timing detector developed by the TOTEM Collaboration for the Roman Pots (RPs) to measure the Time-Of-Flight (TOF) of the protons produced in central diffractive interactions at the LHC. The measurement of the TOF of the protons allows the determination of the longitudinal position of the proton interaction vertex and its association with one of the vertices reconstructed by the CMS detectors. The TOF detector is based on single crystal Chemical Vapor Deposition (scCVD) diamond plates and is designed to measure the protons TOF with abou…
Photon induced processes can be used as a sensitive probe of new physics searches and can be studied using exclusive processes. These processes lead to unprecedented sensitivities on quartic anomalous couplings between photons and W and Z bosons, and new physics searches. By tagging the leading proton from the hard interaction, the Precision Proton Spectrometer (PPS) provides an increased sensitivity to select exclusive processes. PPS is designed to operate in standard high-luminosity runs at the LHC to perform measurements of e.g. the quartic gauge couplings and search for rare exclusive proc…
A search for exclusive two-photon production via photon exchange in proton-proton collisions, pp $\to$ p$γγ$p with intact protons, is presented. The data correspond to an integrated luminosity of 9.4 fb$^{-1}$ collected in 2016 using the CMS and TOTEM detectors at a center-of-mass energy of 13 TeV at the LHC. Events are selected with a diphoton invariant mass above 350 GeV and with both protons intact in the final state, to reduce backgrounds from strong interactions. The events of interest are those where the invariant mass and rapidity calculated from the momentum losses of the forward-movin…
We plan to add high precision tracking- and timing-detectors at z = +/- 240 m to CMS to study exclusive processes p + p -- p + X + p at high luminosity. This enables the LHC to be used as a tagged photon-photon collider, with X = l+l- and W+W-, and as a "tagged" gluon-gluon collider (with a spectator gluon) for QCD studies with jets. A second stage at z = 240 m would allow observations of exclusive Higgs boson production.
We present a search for supersymmetry (SUSY) in the fully hadronic final state with the CMS detector at the LHC. This final state contains at least two jets and a significant transverse energy imbalance due to neutralinos escaping detection. The background to all-hadronic signature arise from QCD multijet production, ttbar and electroweak boson+jet production. These background can be estimated by utilizing a data-driven approach using events thus enabling a possible discovery of SUSY in the early physics data. In addition to the generic search, we also present an analysis which utilizes a new …
Central exclusive and semiexclusive production of $π^+π^-$ pairs is measured with the CMS detector in proton-proton collisions at the LHC at center-of-mass energies of 5.02 and 13 TeV. The theoretical description of these nonperturbative processes, which have not yet been measured in detail at the LHC, poses a significant challenge to models. The two pions are measured and identified in the CMS silicon tracker based on specific energy loss, whereas the absence of other particles is ensured by calorimeter information. The total and differential cross sections of exclusive and semiexclusive cent…
We investigate the prospects for Central Exclusive Diffractive (CED) production of MSSM Higgs bosons at the LHC using forward proton detectors (FPD) proposed to be installed 220 m and 420 m from ATLAS and CMS detectors. We summarize the situation after the first and very successful data taking period of the LHC. The discovery of a Higgs boson and results from searches for additional MSSM Higgs bosons from the ATLAS and CMS, have recently led to a proposal of new low-energy MSSM benchmark scenarios. The CED signal cross section for the process H -> bb and its backgrounds are estimated in these …
A search for exclusive or semi-exclusive photon pair production, pp to p(*) + photon pair + p(*) (where p(*) stands for a diffractively-dissociated proton), and the observation of exclusive and semi-exclusive electron pair production, pp to p(*) + ee + p(*), in proton-proton collisions at sqrt(s) = 7 TeV, are presented. The analysis is based on a data sample corresponding to an integrated luminosity of 36 inverse picobarns recorded by the CMS experiment at the LHC at low instantaneous luminosities. Candidate photon pair or electron pair events are selected by requiring the presence of two phot…
Exclusive dilepton production occurs with high cross section in gamma-mediated processes at the LHC. The pure QED process $γγ\rightarrow\ell^+\ell^-$ provides the conditions to study particle production with masses at the electroweak scale. By tagging the leading proton from the hard interaction, the Precision Proton Spectrometer (PPS) provides an increased sensitivity to selecting exclusive processes. PPS is a detector system to add tracking and timing information at approximately 210~m from the interaction point around the CMS detector. It is designed to operate at high luminosity with up to…
A measurement is presented of the exclusive and semi-exclusive production of charged pion pairs in proton-proton collisions, pp to p(p*) + $π^+π^-$ + p(p*) here the $π^+π^-$ pair is emitted at central rapidities, and the scattered protons stay intact (p) or diffractively dissociate (p*) without detection. The measurement is performed with the CMS detector at the LHC, using a data sample corresponding to an integrated luminosity of 450 inverse microbarns collected at a center-of-mass energy of 7 TeV. The dipion cross section, measured for single-pion transverse momentum pt >0.2 GeV and rapidity…
There is a rich program of forward physics measurements within the CMS Collaboration covering a wide range of topics. In many cases there is a connection to quantities and effects relevant for very high energy cosmic ray interaction. Some of the recent measurements in the fields of exclusive final states, low-pT inclusive and diffractive cross sections, underlying event, multi parton interactions, double parton scattering, final state particle correlations and minimum bias results are briefly summarized here.
Forward physics with CMS at the LHC covers a wide range of physics subjects, including very low-x_Bj QCD, underlying event and multiple interactions characteristics, gamma-mediated processes, shower development at the energy scale of primary cosmic ray interactions with the atmosphere, diffraction in the presence of a hard scale and even MSSM Higgs discovery in central exclusive production. Selected feasibility studies to illustrate the forward physics potential of CMS are presented.
The CMS Collaboration intends to pursue the study of central exclusive production (CEP) events, pp $\to$ pXp, at the High-Luminosity LHC (HL-LHC) by means of a new near-beam proton spectrometer. In CEP events, the state X is produced at central rapidities, and the scattered protons do not leave the beam pipe. The kinematics of X can be fully reconstructed from that of the protons, which gives access to final states otherwise not visible. CEP allows unique sensitivity to physics beyond the standard model, e.g. in the search for anomalous quartic gauge couplings, axion-like particles, and in gen…
The CERN Large Hadron Collider (LHC) started operation a few months ago. The machine will deliver proton-proton and nucleus-nucleus collisions at energies as high as sqrt(s)=14 TeV and luminosities up to L~10^{34} cm^{-2}s^{-1}, never reached before. The main open scientific questions that the seven LHC experiments -- ATLAS, CMS, ALICE, LHCb, TOTEM, LHCf and MOEDAL -- aim to solve in the coming years are succinctly reviewed.
