Lhc constraints

HEP Experiments. Learn more. Mansi Dhuria Ahmedabad, Phys. Chandan Hati Ahmedabad, Phys. Lab and Indian Inst. Raghavan Rangarajan Ahmedabad, Phys. Utpal Sarkar Ahmedabad, Phys. Published in: JCAP 09 DOI: Citations per year 0 2 4 6 8. Abstract: IOP. Note: 8 pages, 7 figures, revised version. References Figures Pati Maryland U. D 10Phys. D 11 erratum. Mohapatra City Coll. Jogesh C. D 11 Senjanovic City Coll. Rabindra N. D 12 Vardan Khachatryan Yerevan Phys. C 74 11An interesting class of models posits that the dark matter is a Majorana fermion which interacts with a quark together with a colored scalar mediator.

Such a theory can be tested in direct detection experiments, through dark matter scattering with heavy nuclei, and at the LHC, via jets and missing energy signatures. Motivated by the fact that such theories have spin-independent interactions that vanish at tree level, we examine them at one loop along with RGE improvement to resum large logsand find that despite its occurrence at a higher order of perturbation theory, the spin-independent scattering searches typically impose the strongest constraints on the model parameter space.

We further analyze the corresponding LHC constraints at one loop and find that it is important to take them into account when interpreting the implications of searches for jets plus missing momentum on this class of models, thus providing the corresponding complementary information for this class of models. Many UC-authored scholarly publications are freely available on this site because of the UC's open access policies.

Let us know how this access is important for you. Skip to main content. UC Irvine. Email Facebook Twitter. Direct detection and LHC constraints on a t-channel simplified model of Majorana dark matter at one loop. Abstract An interesting class of models posits that the dark matter is a Majorana fermion which interacts with a quark together with a colored scalar mediator.

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LHC at 10: the physics legacy

Enter the password to open this PDF file:. Cancel OK. File name:. File size:. Title:. Author:. Subject:. Keywords:. Creation Date:. Modification Date: .Physicists have been searching for signs of SUSY for over forty years, so far without success, which makes us think that SUSY particles — should they exist — are also heavier than particles in the Standard Model.

A particularly challenging case is where the sleptons superpartners of the electron and muon decay directly to the lightest SUSY partner the LSP that has a mass very close to the slepton mass. The challenge in searching for compressed sleptons is that the events are difficult to distinguish from Standard Model processes.

Fortunately, there are features of SUSY events that help them to stand out. The results are therefore used to set limits on slepton masses. Physics Briefing.

Higgs boson examined as source of dark matter at the LHC

Solid histograms indicate Standard Model background processes, points with error bars indicate the data, and the dashed lines indicate simulated SUSY events. The bottom plot shows the ratio of the data to the total Standard Model background. Figure 2: Limits on slepton production using events with missing momentum and two electrons or muons.

The mass of the slepton is on the horizontal axis, while the difference in mass between the slepton and the LSP is shown on the vertical axis. The dashed and solid lines show the expected limits assuming no signal and observed limits, respectively, where models to the left of the red line are excluded.

Physics Briefing - 27 May Fantastic decays and where to find them. Physics Briefing - 18 Feb Searching for natural supersymmetry using novel techniques.How the injector chain has contributed to increase the luminosity of the proton-lead ion run. By Django Manglunki for the injector team. Two different injector chains boost and deliver the two different types of particles to the LHC.

The challenge for the injector complex is twofold. Firstly, the injection pattern of the protons must match with that of the lead ions, in order to maximise the number of colliding bunches in the LHC.

Oxford Sparks: A quick look around the LHC

The ideal situation would be to have the same number of bunches and the same bunch spacing for both protons and lead ions. However, the lead ion injection technique sets a constraint.

LEIR and the PS can only provide the SPS with a lead ion beam consisting of four bunches spaced by nanoseconds nsa different pattern than in normal p-p operations where the proton beam consists of 72 bunches spaced by 25 ns. Secondly, the intensity of the proton beam must also be reduced to correspond to that of the lead ions.

For p-Pb operations, the proton bunches need to be five times less intense than usual. The best possible match that the injector team has found is to inject a train of two batches each consisting of 18 bunches of protons and a train of seven batches consisting of four bunches of lead ions see picture for more details. Since the beginning of the run, the Pb injectors have delivered an intensity three times greater than the original design value.

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At the time of writing, the LHC is still on course to achieve all the physics goals of this run, in spite of all the technical mishaps encountered, such as a power cut last week and a quench on 24 November. News News Topic: Accelerators. The injection scheme for the proton beam upper part of the picture starts with the PSB, which first sends four bunches to the PS, followed by two more 1.

In the PS, the bunches are then split in three and are spaced by ns. The accelerated beam is extracted towards the SPS and traverses a 1-mm thick aluminium foil, which strips the ions of their 28 remaining electrons. Due to the different bunch spacings, only the 27 blue bunches collide in each train.

Each operation is repeated 20 times to fill both rings of the LHC. LHC report. Related Articles. LHC Report: entering the last week of the hea LHC report: make way for the heavy ions. Also On Accelerators.

lhc constraints

The first accelerators are back in action. Electricity transmission reaches even higher LS2 Report: A new schedule. Superconducting magnets of the future in theDark matter is aptly named.

It emits no light and interacts with visible matter only via gravity. But dark matter might be only the tip of an invisible universe of unknown forces. Evidence for dark photons would be a game changer, revealing that dark matter leads a secret life that is much more complex than assumed by most theories. The latest search for dark photons at the Large Hadron Collider, however, has come up empty.

Nevertheless, the results narrow the range of possible values for the strength of the coupling between dark photons and electromagnetic fields. Proton collisions are one possible avenue for creating dark photons that then decay, either promptly or after some time, into muons and antimuons. The team running the Large Hadron Collider beauty LHCb detector combed through proton-proton collision data collected in and found no evidence for an excess of muon-antimuon pairs that could indicate dark photons.

However, the researchers were able to tighten constraints on the electromagnetic coupling for promptly decaying dark photons in the The results bode well for the upcoming analysis of experiments performed inwhich focused on finding decay products of dark photons in the lower mass range.

The researchers anticipate that bythe experiment will be more sensitive to dark-photon decays by a factor of at least several hundred. This research is published in Physical Review Letters. The CMS Collaboration confirms that certain particle-smashing events produce three massive bosons. An analysis of more thanmuon neutrino detections provides no evidence of sterile neutrinos—a finding at odds with other experiments.

LHC constraints on NLSP gluino and dark matter neutralino in Yukawa unified models

Aaij et al. LHCb Collaboration Phys. Particles and Fields. Particles and Fields No Sterile Neutrinos from Eight Years of IceCube September 30, An analysis of more thanmuon neutrino detections provides no evidence of sterile neutrinos—a finding at odds with other experiments. Sign up to receive weekly email alerts from Physics.Abdallah, S.

lhc constraints

We also analyze the thermal relic abundance of lightest neutralino, which is the Lightest Supersymmetric Particle LSP. Within this region, we emphasize that the spin-independent scattering cross section of the LSP with a proton is less than the latest Large Underground Xenon LUX limit by at least two orders of magnitude.

The most recent observations by the Planck satellite confirmed that The most simple supersymmetric extension of the SM, which is the most widely studied, is known as the MSSM [ 4 — 11 ]. In this model, certain universality of soft SUSY breaking terms is assumed at grand unification scale. Therefore, the SUSY spectrum is determined by the following four parameters: universal scalar massuniversal gaugino massuniversal trilinear couplingand the ratio of the vacuum expectation values of Higgs bosons.

In addition, due to -parity conservation, SUSY particles are produced or destroyed only in pairs and therefore the LSP is absolutely stable, implying that it might constitute a possible candidate for DM, as first suggested by Goldberg in [ 12 ].

lhc constraints

So although the original motivation of SUSY has nothing to do with the DM problem, it turns out that it provides a stable neutral particle and, hence, a candidate for solving the DM problem. Moreover, the relic density data [ 1 ] and upper limits on the DM scattering cross sections on nuclei LUX [ 19 ] and other direct detection experiments [ 2021 ] impose stringent constraints on the parameter space of the MSSM [ 22 — 25 ]. In fact, combining the collider, astrophysics, and rare decay constraints [ 26 — 36 ] almost rules out the MSSM.

It is tempting therefore to explore well motivated extensions of the MSSM, such as NMSSM [ 3738 ] and BLSSM [ 3940 ], which may alleviate the little hierarchy problem of the MSSM through additional contributions to Higgs mass [ 373841 ] and also provide new DM candidates [ 42 — 45 ] that may account for the relic density with no conflict with other phenomenological constraints.

lhc constraints

Finally, we show that if one assumes nonstandard scenario of cosmology with low reheating temperature, where the LSP may reach equilibrium before the reheating time, then the relic abundance constraints on can be significantly relaxed. The paper is organized as follows. In Section 2we briefly introduce the MSSM and study the constraints on plane from Higgs and gluino mass experimental limits. In Section 3we study the thermal relic abundance of the LSP in the allowed region of parameter space.

We show that the combined LHC and relic abundance constraints rule out most of the parameter space except the case of very large. Section 4 is devoted to nonthermal scenario of DM and how it can relax the constraints imposed on MSSM parameter space. Finally, we give our conclusions in Section 5. The particle content of the MSSM is three generations of chiral quark and lepton superfields; the vector superfields are necessary to gauge gauge of the SM, and two chiral doublet Higgs superfields.

The introduction of a second Higgs doublet is necessary in order to cancel the anomalies produced by the fermionic members of the first Higgs superfield and also to give masses to both up and down type quarks.

The interactions between Higgs and matter superfields are described by the superpotential Here, contains s quark doublets andare the corresponding singlets, s lepton doublets and singlets reside in andrespectively. Further, due to the fact that Higgs and lepton doublet superfields have the same quantum numbers, we have additional terms that can be written as These terms violate baryon and lepton number explicitly and lead to proton decay at unacceptable rates.

To forbid these terms, a new symmetry, called -parity, is introduced, which is defined aswhere and are baryon and lepton number and is the spin. There are two remarkable phenomenological implications of the presence of -parity: i SUSY particles are produced or destroyed only in pair; ii the LSP is absolutely stable and, hence, it might constitute a possible candidate for DM. These terms are defined asthe universal scalar soft mass,the universal gaugino mass,the universal trilinear coupling,and the bilinear coupling the soft mixing between the Higgs scalars.

In order to discuss the physical implication of soft SUSY breaking at low energy, we need to renormalize these parameters from down to electroweak scale, which has been performed using SARAH [ 46 ], and the spectrum has been calculated using SPheno [ 4748 ]. Two of these free parameters, andcan be determined by the electroweak breaking conditions: Thus, the MSSM has only four independent free parameters,besides the sign ofwhich determine the whole spectrum.The Higgs boson plays a crucial role in the search for dark matter at the Large Hadron Collider.

Presence of such particles in the collision debris would create an energy imbalance with visible particles, which can be measured. The data show no excess of such characteristic events over the expected background. These findings place the strongest limits so far on Higgs transformations to such invisible particles. No particles of this substance have been observed in a laboratory. Collision events in which a Higgs is produced through vector-boson fusion contain additional conical jets of particles directed towards the forward regions of ATLAS, close to the LHC beam pipe.

The missing energy resulting from the individual particles would, on the other hand, be aligned towards the vertical plane perpendicular to the beam pipe. Combining these two characteristics gives scientists a unique signature in the quest for dark matter. Although no excess was observed, the search provided important constraints on low-mass dark matter, which complement direct searches for dark matter performed at other facilities.

It was also an important demonstration of the novel techniques that scientists are applying in research at the LHC. The Higgs boson, discovered inhas quickly evolved into an invaluable means of searching for signs of physics beyond the Standard Model of particle physics.

News News Topic: Physics. The experimental signature of two particle jets yellow cones and large missing energy dashed line is shown Image: CERN. Related Articles. CERN experiments announce first indications o Also On Physics. CMS sees evidence of top quarks in collisions LHCb sees new form of matter—antimatter asymm A roadmap for the future.

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