SND@LHC是一项紧凑实验，将探测LHC上重夸克产生的高能中微子，覆盖赝快度区间7.2<η<8.6。该混合系统包含核乳胶与电子探测器，能区分全部三种ν味道，从而为探索极前向区域的粲产生物理提供了独特机遇。第一阶段目标是在LHC Run 3期间运行探测器，共收集150 fb⁻¹数据。电子子探测器于夏季组装完成，近期已在测试束中运行。
英文摘要：
SND@LHC is a compact experiment that will detect high energy neutrinos produced by heavy flavour quarks at the LHC in the pseudo-rapidity region 7.2 $< η<$ 8.6. It is an hybrid system, comprising nuclear emulsions and electronic detectors, that allows all three $ν$ flavours to be distinguished, thus opening an unique opportunity to probe the physics of charm production in the very forward region. The first phase aims at operating the detector throughout LHC Run 3 collecting a total of 150 fb$^{-1}$. The electronic subdetectors were assembled in the summer and recently operated in test beams.
The LHCb RICH system provides hadron identification over a wide momentum range (2-100 GeV/c). This detector system is key to LHCb's precision flavour physics programme, which has unique sensitivity to physics beyond the standard model. This paper reports on the performance of the LHCb RICH in Run II, following significant changes in the detector and operating conditions. The changes include the refurbishment of significant number of photon detectors, assembled using new vacuum technologies, and the removal of the aerogel radiator. The start of Run II of the LHC saw the beam energy increase to …
I discuss the development of high precision timing detectors for high momentum protons at the LHC, and their application in studying exclusive Higgs boson production.
The limitation of the detection rate of standard bakelite resistive plate chambers (RPC) used as muon detectors in the LHC experiments has prevented the use of such detectors in the high rate regions in both CMS and ATLAS detectors. One alternative to these detectors are RPCs made with low resistivity glass plates ($10^{10} {\rm Ω.cm}$), a beam test at DESY has shown that such detectors can operate at few thousand Hz/cm$^2$ with high efficiency(> 90%)
We discuss a CMS eXtension for Studying Energetic Neutrinos (CMS-XSEN). Neutrinos at the LHC are abundant and have unique features: their energies reach out to the TeV range, and the contribution of the τ flavour is sizeable. The measurement of their interaction cross sections has much physics potential. The pseudorapity range 4<|η|<5 is of particular interest since leptonic W decays provide an additional contribution to the neutrino flux from b and c production. A modest detector of 4.1x$10^{27}$ nucleons/cm$^{2}$, placed in the LHC tunnel, 25 m from the interaction point, around the focusing…
XSEN (Cross Section of Energetic Neutrinos) is a small experiment designed to study, for the first time, neutrino-nucleon interactions (including the tau flavour) in the 0.5-1 TeV neutrino energy range. The detector will be installed in the decommissioned TI18 tunnel and uses nuclear emulsions. Its simplicity allows construction and installation before the LHC Run 3, 2021-2023; with 150/fb in Run3, the experiment can record up to two thousand neutrino interactions, and up to a hundred tau neutrino events. The XSEN detector intercepts the intense neutrino flux, generated by the LHC beams collid…
Intense and collimated neutrino beams are produced by charm and beauty particle decays from proton-proton collisions at the LHC. A neutrino experiment would be run parasitically without interrupting the LHC physics program during the collider run. We estimate the neutrino fluxes from proton-proton collisions at $\sqrt{s}=14$ TeV of the LHC with the designed luminosity, $10^{34} \lumi$. By mounting about 200 tons of fiducial volume of a neutrino detector at 300 $\m$ away from the interaction point, about 150,000 of charged current neutrino events per year can be observable.
We discuss an experiment to investigate neutrino physics at the LHC in Run 3, with emphasis on tau flavour. As described in our previous paper [arXiv:1903.06564v1], the detector can be installed in the decommissioned TI18 tunnel, about 480 m downstream the ATLAS cavern, after the first bending dipoles of the LHC arc. In that location, the prolongation of the beam Line-of-Sight from Interaction Point IP1 to TI18 traverses about 100 m of rock. The detector intercepts the intense neutrino flux, generated by the LHC beams colliding in IP1, at large pseudorapidity eta, where neutrino energies can e…
We study the sensitivity of displaced vertex searches for heavy neutrinos produced in W boson decays in the LHC detectors ATLAS, CMS and LHCb. We also propose a new search that uses the muon chambers to detect muons from heavy neutrino decays outside the tracker. The sensitivity estimates are based on benchmark models in which the heavy neutrinos mix exclusively with one of the three Standard Model generations. In the most sensitive mass regime the displaced vertex searches can improve existing constraints on the mixing with the first two Standard Model generations by more than four orders of …
Silicon Drift Detectors (SDD) equip the two central layers of the Inner Tracking System of the ALICE experiment at the LHC. Main results of systematic studies of detector performance including noise, gain, drift speed and charge collection measurements will be reported
The search for the Higgs boson produced by Vector Boson Fusion (VBF) where the Higgs decays into W pairs and thence to leptons plus neutrinos is discussed at the Monte Carlo generator level. In particular, the cuts which are applied in order to reduce backgrounds are almost exactly those used to extract the VBF production of Z bosons.
We briefly review the current status and future prospects of testing the low-scale seesaw models of neutrino mass generation at the energy frontier, with particular emphasis on the ongoing searches at the LHC.
We propose the operation of \textbf{LEvEL}, the Low-Energy Neutrino Experiment at the LHC, a neutrino detector near the Large Hadron Collider Beam Dump. Such a detector is capable of exploring an intense, low-energy neutrino flux and can measure neutrino cross sections that have previously never been observed. These cross sections can inform other future neutrino experiments, such as those aiming to observe neutrinos from supernovae, allowing such measurements to accomplish their fundamental physics goals. We perform detailed simulations to determine neutrino production at the LHC beam dump, a…
This proceeding explores some of the questions that connect the LHC and neutrino experiments: What is the origin of mass? What is the meaning of flavor? Is there direct evidence of new forces or particles? The neutrino program investigating these questions is large and diverse. The strategy here, to narrow the discussion, is to focus on relatively new ideas for experiments that may be less known within the LHC community.
We discuss here future neutrino detectors with physics goals ranging from the eV to the EeV scale. The focus is on future enabling technologies for such detectors, rather than existing detectors or those under construction. The report includes methodologies across the broad spectrum of neutrino physics: liquid noble and other cryogenic detectors, includin LAr and LXe TPCs; photon-based detectors including technologies enabling hybrid Cherenkov/scintillation detectors; low-threshold detectors which use a wide variety of technologies to probe physics like coherent neutrino-nucleus scattering or …
We study a new production mechanism for heavy neutrinos at the LHC, which dominates over the usually considered $s$-channel $W$-exchange diagram for heavy-neutrino masses larger than 100 - 200 GeV. The new mechanism is infrared-enhanced by $t$-channel $Wγ$-fusion processes. This has important implications for experimental tests of the seesaw mechanism of neutrino masses, and in particular, for the ongoing heavy neutrino searches at the LHC. We find that the direct collider limits on the light-to-heavy neutrino mixing can be significantly improved, when this new production channel is properly t…
We consider the possibility to detect right-handed neutrinos, which are mostly singlets of the Standard Model gauge group, at future accelerators. Substantial mixing of these neutrinos with the active neutrinos requires a cancellation of different contributions to the light neutrino mass matrix at the level of 10^{-8}. We discuss possible symmetries behind this cancellation and argue that they always lead to conservation of total lepton number. Light neutrino masses can be generated by small perturbations violating these symmetries. In the most general case, LHC physics and the mechanism of ne…
We explore the complementarity between LHC searches and neutrino experiments in probing neutrino non-standard interactions. Our study spans the theoretical frameworks of effective field theory, simplified model and an illustrative UV completion, highlighting the synergies and distinctive features in all cases. We show that besides constraining the allowed NSI parameter space, the LHC data can break important degeneracies present in oscillation experiments such as DUNE, while the latter play an important role in probing light and weakly coupled physics undetectable at the LHC.
Sterile neutrinos with masses in the range (1-100) GeV, have been searched for in a variety of experiments. Here, we discuss the prospects to search for sterile neutrinos at the LHC using displaced vertices. Two different cases are discussed: (i) the standard model extended with sterile neutrinos and (ii) right-handed neutrinos in a left-right symmetric extension of the standard model. A dedicated displaced vertex search will allow to probe parts of the parameter space not accessible to other searches, but will require large luminosity in both cases.
The existence of heavy neutrinos mediating neutrino masses via a type-I seesaw can be directly probed at the LHC, or indirectly in rare lepton flavor-violating processes. The synergy between these two approaches requires a direct measurement of the heavy neutrino couplings. We discuss a strategy to perform such measurements at the LHC in the context of left-right symmetric models, which is also applicable to other models implementing a type-I or type-III seesaw. We demonstrate that the ambiguities in the determination of the heavy neutrino mixing parameters can be resolved by performing an exc…
We discuss lepton flavour violating processes induced in the production and decay of heavy right-handed neutrinos at the LHC. Such particles appear in left-right symmetrical extensions of the Standard Model as the messengers of neutrino mass generation, and can have masses at the TeV scale. We determine the expected sensitivity on the right-handed neutrino mixing matrix, as well as on the right-handed gauge boson and heavy neutrino masses. By comparing the sensitivity of the LHC with that of searches for low energy LFV processes, we identify favourable areas of the parameter space to explore t…
Heavy neutrinos at the TeV scale have been searched for at the LHC in the context of left-right models, under the assumption that they couple to the electron, the muon, or both. We show that current searches are also sensitive to heavy neutrinos coupling predominantly to the tau lepton, and present limits can significantly constrain the parameter space of general flavour mixing.
We consider right-handed neutrino pair production in generic $Z^\prime$ models. We propose a new, model-independent analysis using final states containing a pair of same-sign muons. A key aspect of this analysis is the reconstruction of the RH neutrino mass, which leads to a significantly improved sensitivity. Within the $U(1)_{(B-L)_{3}}$ model, we find that at the HL-LHC it will be possible to probe RH neutrino masses in the range $0.2\lesssim M_{N_R} \lesssim 1.1\,$TeV.
The significant neutrino flux at high rapidity at the LHC motivates dedicated forward detectors to study the properties of neutrinos at TeV energies. We investigate magnetic dipole interactions between the active neutrinos and new sterile states at emulsion and liquid argon experiments that could be located in a future Forward Physics Facility (FPF) downstream of the ATLAS interaction point. The up-scattering of neutrinos off electrons produces an electron recoil signature that can probe new regions of parameter space at the High Luminosity LHC (HL-LHC), particularly for liquid argon detectors…
The forward proton detectors, already existing at the LHC, are considered in the context of heavy ion collisions. It is shown that such detectors have the potential to measure nuclear debris originating from spectator nucleons. The geometric acceptance for different nuclei is studied, and how it is affected by the motion of the nucleons in the nucleus and by the experimental conditions. A possibility of extending the acceptance region is discussed.
The LHC detectors are well into their construction phase. The LHC schedule shows first beam to ATLAS and CMS in 2007. Because the LHC accelerator has begun to plan for a ten fold increase in LHC design luminosity (the SLHC or super LHC) it is none too soon to begin to think about the upgrades which will be required of the present LHC detectors. In particular, the tracking systems of ATLAS and CMS will need to be completely rebuilt. Given the time needed to do the R&D, make prototypes, and construct the new detectors and given the accelerator schedule for the SLHC, work needs to begin rather so…
We study how nonstandard neutrino interactions (NSI) may be probed by a combination of coherent elastic neutrino-nucleus scattering, neutrino oscillation and collider data, from COHERENT, DUNE, T2HK and the high-luminosity (HL) LHC. We focus on NSI induced by a new flavored gauge boson $Z'$ in a generic anomaly-free ultraviolet-complete model. For $Z'$ masses above 10 GeV, the HL-LHC has the best sensitivity regardless of the flavor structure of the model. For masses between 0.01 GeV-10 GeV, current LHCb data and future COHERENT data have the best sensitivity unless the $Z'$ couplings to the f…
Neutrino fluxes at high rapidity and at high energy are sensitive to QCD dynamics of heavy-flavor production in kinematic regions where measurements have not yet been made. The FASER$ν$ and SND@LHC experiments scheduled for Run 3 at the LHC and the proposed Forward Physics Facility with a suite of experiments during the High-Luminosity LHC phase will probe neutrinos at high pseudorapidity. This short paper reports on recent evaluations of the prompt $ν_τ+\barν_τ$ and $ν_e+\barν_e$ double-differential cross sections in $pp$ collisions at the Large Hadron Collider from the production and decays …
The OPERA collaboration has reported the observation of superluminal muon neutrinos, whose speed $v_ν$ exceeds that of light $c$, with $(v_ν- c)/c \simeq 2.5 \times 10^{-5}$. In a recent work, Cohen and Glashow (CG) have refuted this claim by noting that such neutrinos will lose energy, by pair-emission of particles, at unacceptable rates. Following the CG arguments, we point out that pair-emissions consistent with the OPERA anomaly can lead to detectable signals from decays of highly boosted top quarks at the LHC, allowing an independent test of the superluminal neutrino hypothesis.
Theoretical predictions of the prompt atmospheric neutrino flux have large uncertainties associated with charm hadron production, by far the dominant source of prompt neutrinos in the atmosphere. The flux of cosmic rays, with its steeply falling energy spectrum, weights the forward production of charm in the evaluation of the atmospheric neutrino flux at high energies. The current LHCb experiment at CERN constrains charm production in kinematic regions relevant to the prompt atmospheric neutrino flux. The proposed Forward Physics Facility has additional capabilities to detect neutrino fluxes f…
We present recent work performed in ATLAS on techniques used to reconstruct the decays of SUSY particles at the LHC. We concentrate on strategies to be applied to the first fb-1 of LHC data.
The capabilities of the ATLAS and CMS detectors being prepared for the LHC are reviewed. Examples of physics signals accessible during early running and during mature high luminosity LHC operation are examined. The planning and options for the LHC and these detectors to increase the luminosity to 10^{35}cm^{-2}s^{-1} is presented. This upgrade, entitled the Super LHC (SLHC), would occur in the next decade. The resulting physics scope is discussed.
Seesaw models with a small lepton number breaking can naturally accommodate electroweak-scale pseudo-Dirac neutrinos with a sizable mixing with the active neutrinos, while satisfying the light neutrino oscillation data. Due to the smallness of the lepton number breaking parameter, the 'smoking gun' collider signature of same-sign dileptons is suppressed, and the heavy neutrinos in these models would manifest at the LHC dominantly through lepton number conserving trilepton final states. Using the recent CMS results for anomalous production of multilepton events at $\sqrt{s}$=8 TeV LHC with an i…
We study the LHC sensitivity to probe a long-lived heavy neutrino $N$ in the context of $Z'$ models. We focus on displaced vertex signatures of $N$ when pair produced via a $Z'$, decaying to leptons and jets inside the inner trackers of the LHC experiments. We explore the LHC reach with current long-lived particle search strategies for either one or two displaced vertices in association with hadronic tracks or jets. We focus on two well-motivated models, namely, the minimal $U(1)_{B-L}$ scenario and its $U(1)_{X}$ extension. We find that searches for at least one displaced vertex can cover a s…
Observation of lepton number ($L$) violation by two units at colliders would provide evidence for the Majorana nature of neutrinos. We study signals of $L$-violation in the context of two popular models of neutrino masses, the type-II seesaw model and the Zee model, wherein small neutrino masses arise at the tree-level and one-loop level, respectively. We focus on $L$-violation signals at the LHC arising through the process $pp \to \ell^{\pm}\ell^{\prime \pm}$ + jets within these frameworks. We obtain sensitivity to $L$-violation in the type-II seesaw model for triplet scalar masses up to 700 …
We propose and investigate a novel, minimal, and experimentally testable framework for baryogenesis, dubbed dexiogenesis, using baryon number violating effective interactions of right-handed Majorana neutrinos responsible for the seesaw mechanism. The distinct LHC signature of our framework is same-sign top quark final states, possibly originating from displaced vertices. The region of parameters relevant for LHC phenomenology can also yield concomitant signals in nucleon decay experiments. We provide a simple ultraviolet origin for our effective operators, by adding a color-triplet scalar, wh…
The Majorana neutrino in type-I seesaw and the pseudo-Dirac neutrinos in the inverse seesaw can have sizable mixings with the light neutrinos in the standard model (SM), through which the heavy neutrinos can be produced at the Large Hadron Collider (LHC). In producing the heavy neutrinos we study a variety of initial states such as quark-quark, quark-gluon and gluon-gluon as well as photon mediated processes. For the Majorana heavy neutrino production we consider same-sign di-lepton plus di-jet as the signal events. Using the recent ATLAS and CMS data at $\sqrt{s}=$ 8 TeV with 20.3 fb$^{-1}$ a…
In the inverse see-saw model the effective neutrino Yukawa couplings can be sizable due to a large mixing angle between the light $(ν)$and heavy neutrinos $(N)$. When the right handed neutrino $(N)$ can be lighter than the Standard Model (SM) Higgs boson $(h)$. It can be produced via the on-shell decay of the Higgs, $h\to Nν$ at a significant branching fraction at the LHC. In such a process $N$ mass can be reconstructed in its dominant $N\rightarrow W \ell$ decays. We perform an analysis on this channel and its relevant backgrounds, among which the $W+$jets background is the largest. Consideri…
New measurements from ATLAS at the LHC are presented on the total cross section at $\sqrt{s}=8$ TeV from elastic scattering using the ALFA sub-detector and on the inelastic cross section at $\sqrt{s}=13$ TeV using the MBTS sub-detector.
Contrary to the see-saw models, extended Higgs sectors leading to radiatively-induced neutrino masses do require the extra particles to be at the TeV scale. However, these new states have often exotic decays, to which experimental LHC searches performed so far, focused on scalars decaying into pairs of same-sign leptons, are not sensitive. In this paper we show that their experimental signatures can start to be tested with current LHC data if dedicated multi-region analyses correlating different observables are used. We also provide high-accuracy estimations of the complicated Standard Model b…
We show that in TeV-scale left-right (L-R) symmetric seesaw models, there are new dominant contributions to the collider signals of heavy Majorana neutrinos arising from the heavy-light neutrino mixing, which directly probe the seesaw matrix in a certain class of models. We propose a way to distinguish this contribution from the widely discussed one that only probes the Majorana nature of the heavy right-handed neutrinos, by analyzing some simple kinematical variables. We find that in this class of L-R seesaw models the existing LHC data already yield slightly stronger constraints on the heavy…
In light of recent results from the LHC, MEG and neutrino experiments, we revisit the issue of charged lepton flavour violation (LFV) in supersymmetric theories with massive neutrinos, where flavour-violating soft supersymmetry-breaking masses for sleptons are induced naturally by radiative corrections. We link our results to the expectations for neutrino mixing angles in SU(5) enhanced by an abelian flavour symmetry, with particular focus on $θ_{13}$. We focus on the radiative decays $\ell_i \rightarrow \ell_j γ$ and on detection prospects at the LHC and a linear collider (LC). We use supersy…
We investigate the reach at the LHC to probe light sterile neutrinos with displaced vertices. We focus on sterile neutrinos $N$ with masses $m_{N} \sim $ (5-30) GeV, that are produced in rare decays of the Standard Model gauge bosons and decay inside the inner trackers of the LHC detectors. With a strategy that triggers on the prompt lepton accompanying the $N$ displaced vertex and considers charged tracks associated to it, we show that the 13 TeV LHC with $3000$/fb is able to probe active-sterile neutrino mixings down to $|V_{lN}|^2\approx 10^{-9}$, with $l=e,μ$, which is an improvement of up…
Dilepton-jet final states are used to study physical phenomena not predicted by the standard model. The ATLAS discovery potential for leptoquarks and Majorana Neutrinos is presented using a full simulation of the ATLAS detector at the Large Hadron Collider. The study is motivated by the role of the leptoquark in the Grand Unification of fundamental forces and the see-saw mechanism that could explain the masses of the observed neutrinos. The analysis algorithms are presented, background sources are discussed and estimates of sensitivity and the discovery potential for these processes are report…
