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susy is perhaps the most promising candidate for physics beyond the standard model ; it also provides a good test of detector performance . the atlas  @xcite and cms  @xcite collaborations at the cern large hadron collider ( lhc ) have therefore devoted a lot of effort to studying susy signatures and measurements . this talk provides an overview of that work with emphasis on new results since the overviews in ref .   and . the susy cross section at the lhc is dominated by the associated strong production of gluinos and squarks . if @xmath0 parity is conserved , these decay into the lightest susy particle @xmath1 , which escapes the detector , plus quarks , gluons , and perhaps other standard model particles . thus , susy provides signatures containing at least jets and large missing transverse energy @xmath2 . the lhc should be able to observe these signals for @xmath3 and @xmath4 masses up to about @xmath5 with only @xmath6 of integrated luminosity . the challenge at the lhc is not to discover tev - scale susy ( assuming it exists ) but to make precision measurements of masses and other quantities . since the decay products of each susy particle contain an invisible @xmath1 , no mass peaks can be reconstructed directly . instead , masses must be inferred  @xcite from kinematic endpoints and other properties of the events . developing methods to do this has been a main emphasis of the studies to date . typically , events are simulated for a particular susy model and for the standard model backgrounds using a parton shower monte carlo program such as herwig  @xcite , isajet  @xcite , or pythia  @xcite , the detector response is simulated using a fast parameterization , cuts are made to give a good signal / background , and various kinematic distributions are reconstructed . a number of examples are presented below . since @xmath3 and @xmath4 are strongly produced , their cross sections are comparable to qcd at the same @xmath7 . if @xmath0 parity is conserved , their decays produce distinctive events with large @xmath2 . a typical analysis requires at least four jets with @xmath8 and @xmath9 and plots as a measure of @xmath7 the quantity @xmath10 for large @xmath11 the standard model background is typically 10% of the signal . the reach is thus limited mainly by the @xmath3 and @xmath4 production cross sections and hence masses . this reach is shown for the minimal sugra model in fig . [ catania18 ] . note that the sensitivity for one month at 10% of design luminosity is about @xmath12 . of course it will take more than one month to understand the detectors , but nevertheless one might hope for an interesting talk at susy08 . squark and gluino decays typically involve one or more intermediate charginos or neutralinos , giving rise to multi - lepton signatures as well as ones involving jets . the reach for such signatures is shown in figure  [ d_denegri_1266c ] . the emergence of the susy signal from the standard model background is illustrated for a typical case in figure  [ tovey02 ] . also shown is the correlation between the peak of the @xmath11 distribution and @xmath13 obviously , however , any such inclusive correlation is model dependent .    while the reach plots in figure  [ catania18 ] apply only to msugra , similar reach in gluino and squark masses should apply to any model in which they decay into an invisible and relatively light @xmath1 . some models are easier . for example , gmsb models with prompt @xmath14 or @xmath15 decays provide additional photon or lepton handles to suppress standard model backgrounds . gmsb models with a quasi - stable @xmath16 provide a penetrating charged particle with @xmath17 that is well measured by the muon detectors . amsb models give few single leptons but larger @xmath2 . if @xmath0 parity is violated via @xmath18 or @xmath19 , there are again additional leptons . perhaps the most difficult case is @xmath0-violation via @xmath20 , giving multiple jets but no @xmath21 jets . the background is poorly known , but it seems likely that one must rely on leptonic cascade decays . in general , however , discovery of gluinos and squarks with masses of order @xmath22 appears straightforward . masses of @xmath23 are of course much more difficult and would probably need a luminosity upgrade . if @xmath0 parity is conserved , then the @xmath1 is invisible and there are no mass peaks . nevertheless , kinematic endpoints allow one to determine mass combinations . the simplest example is the decay    for the dilepton signature , events are selected to have two leptons with ( typically ) @xmath24 and @xmath25 in addition to multiple hard jets and large @xmath2 . then the dominant standard model background is @xmath26 . the background from @xmath26 or from any other standard model source involving two independent decays cancels in the combination @xmath27 . the same is true for two independent chargino decays in msugra , and it is likely to be true in any susy model that avoids @xmath28 and other low - energy constraints .    an opposite - sign , same - flavor dilepton signature can arise from a 2-body cascade decay @xmath29 , from a 3-body @xmath30 decay , or from a decay via a @xmath31 . all three cases are illustrated in figure  [ blois ] . they are clearly distinguished by shape . such endpoints are observable over a significant fraction of the msugra parameter space , as illustrated in figure  [ cmsll ] . in particular , a large part of the msugra parameter space with acceptable cold dark matter has light sleptons and hence enhanced @xmath32 decays . when a longer decay chain can be identified , more combinations of masses can be measured . for example , at msugra point  5 , the dominant source of dileptons is @xmath33 . the gluino is heavier than the squarks , and the hardest jets generally come from the squarks . in such a case , one can form an @xmath34 endpoint and two @xmath35 endpoints in addition to the @xmath32 one  @xcite . in addition , if a lower limit on the @xmath32 mass is imposed , there is also an @xmath36 threshold . all of these distributions after experimental selections are shown in figure  [ camb5new ] . the endpoints and thresholds can all be expressed in terms of the masses involved using elementary kinematics , and they provide enough constraints to determine the masses . the results taking estimated errors into account for the @xmath1 and @xmath37 masses are shown in figure  [ camb15 ] for two models with similar masses . all the masses involved are determined quite accurately as functions of @xmath38 ; in particular the two models can be easily distinguished . the @xmath1 mass is determined to about 10% through its effect on the kinematics even though it is invisible . an alternative approach is to reconstruct @xmath39 momentum assuming that the @xmath1 mass is known and using @xmath40 while this is exact only for a 3-body @xmath41 at the endpoint , it can be used as an approximation elsewhere . an analysis for sugra point b ( @xmath42 , @xmath43 , @xmath44 , @xmath45 , @xmath46 ) using this method looks for @xmath47 . the dilepton distribution after cuts and the reconstructed @xmath48 distribution using @xmath49 are shown in figure  [ tricomi ] . a second @xmath21 can be added to reconstruct the gluino mass ; see ref .  . if the decay @xmath51 is kinematically allowed , it often has a substantial branching ratio . the decay @xmath50 can be reconstructed by selecting events with multiple jets plus large @xmath2 and plotting the mass of pairs of jets tagged as @xmath21 s . the reach for this signature in msugra , shown in figure  [ cmshbb ] , covers a substantial fraction of parameter space . it might well be the discovery mode for the light susy higgs . if @xmath50 can be reconstructed , it can then be combined with jets to determine other masses . in figure  [ p5_mbbj ] for example , the @xmath52 was combined with each of the two hardest jets in the event ; the smaller of these masses should be less than the @xmath53 endpoint . this measurement is less precise than those involving leptons , but it may be useful if the leptonic branching ratios are small . susy events can be much more complex than those for the cases discussed above . an example is the `` focus point '' region : in msugra as @xmath54 becomes large for fixed values of the other parameters , @xmath55 and radiative electroweak symmetry breaking fails . near this boundary , the @xmath1 is dominantly higgsino , leading to acceptable values of cold dark matter  @xcite . the exact location of the focus point region is very sensitive to details of the susy spectrum calculation  @xcite , but such a region surely exists .    in one calculation @xcite the msugra point @xmath56 , @xmath57 , @xmath44 , @xmath45 , @xmath46 is close to the @xmath58 focus point boundary . since the squarks are heavy , susy production is dominated by @xmath59 pairs . the largest @xmath3 branching ratios are calculated  @xcite to be @xmath60 . these decays give events with 1216 jets and leptons ! the methods described previously suffice to find such signals . many of the basic starting points discussed previously also work ; see for example figure  [ c1500mll ] . but sorting out the combinatorial background in such complex events is quite difficult and has not yet been solved . @xmath0-parity violation with @xmath61 , and especially @xmath62 is another example of a susy model with very complex signatures . in such models the signal has very high jet multiplicity  nominally six jets just from the @xmath1 decays  few or no @xmath21 jets that might be used to reduce the combinatorial background , and small @xmath2 . the qcd background for such events is not well known ; the 1-loop qcd corrections to the production of 6 - 10 jets seem unlikely to be calculated even by the end of lhc running . estimates based on qcd shower monte carlo programs suggest that the backgrounds are comparable to the signals , but this is at best a rough estimate .    for such scenarios , therefore , it is probably necessary to rely on susy cascade decays , e.g. , @xmath63 , to provide additional handles to suppress the qcd background . one example that has been studied uses such decays with branching ratios taken from msugra point 5 . even though there are no missing particles , reconstruction is difficult because the jets from the @xmath1 are soft and the mass resolution is only @xmath64 . define the mass combinations @xmath65 ; then the jet resolution largely cancels for @xmath66 , as can be seen in figure  [ camb6a ] . the distributions in figure  [ camrviol ] show reasonable distributions in these variables . these are just two examples of susy scenarios giving complex signatures . such scenarios are certainly possible , and much more work is needed to develop analysis strategies to deal with them . the initial motivation for studying @xmath67 signatures came from the fact that for large regions of msugra parameter space with @xmath68 the only two - body decay modes are @xmath69 and @xmath70 . then these modes have branching ratios close to 100% , and all ssuy decays involve @xmath67 s . such scenarios are disfavored because they tend to give contributions to @xmath71 much larger than observed . low - energy tests of the standard model seem to require that the first two generations of squarks and sleptons be nearly degenerate . this degeneracy is not understood in general but does occur in msugra . even in msugra , however , the third generation of squarks and sleptons is split by renormalization group and left - right mixing effects . thus , study of the third generation is likely to be essential for understanding susy . because of technical constraints , the atlas and cms vertex detectors do not have sufficient resolution to identify @xmath67 decays cleanly . hence , leptonic @xmath67 decays can not be distinguished from prompt leptons , and @xmath67 s can only be identified using narrow , one - prong jets , for which there is substantial qcd background . as can be seen from figure  [ tdr9 - 31 ] , the typical jet rejection is a factor of about 100 for a @xmath67 efficiency of 50% .    for msugra with @xmath72 , @xmath44 , @xmath73 , the only 2-body decays of light gauginos are @xmath74 and @xmath75 . these decays therefore dominate . since there is @xmath2 both from @xmath76 s and from @xmath1 s , the @xmath67 distributions can only be inferred from their hadronic decay products . instead of a sharp @xmath77 edge at @xmath78 , one would observe the distribution shown in figure  [ p6subtracted ] . the visible @xmath67 momentum depends both on the momentum and on the polarization of the parent @xmath67 . the decay @xmath79 is maximally sensitive to the polarization while high - mass decays are rather insensitive to it . a study of the separation of different decay modes has been carried out using a full geant - based simulation of @xmath67 s from susy events in the atlas detector . the visible @xmath67 mass is reconstructed by combining charged tracks and electromagnetic calorimeter cells , exploiting the fine granularity of the calorimeter . the reconstructed masses , figure  [ mtaunew ] , show a good separation of @xmath80 decays and some difference between @xmath81 and @xmath82 decays . the same figure indicates the sensitivity of the @xmath77 mass distribution to a reversal of helicities . in gmsb models the lightest susy particle is the light gravitino @xmath83 . the phenomenology depends on nature and lifetime of the next lightest particle ( nlsp ) , which can be either the @xmath1 or a @xmath16 . decays into @xmath83 lead to more distinctive events and to longer decay chains , such as @xmath84 , that can be used to determine susy masses  @xcite . the lifetime for the nlsp to decay to a @xmath83 is unknown and is an important parameter of the model . short @xmath14 lifetimes can be measured by selecting dalitz decays and using the vertex detector . for @xmath85 the signature is occasional photons that do no point to the primary vertex . the atlas electromagnetic calorimeter was designed to measure photon angles with @xmath86 to improve the @xmath87 mass resolution . it also has good time resolution , @xmath88 . both can be exploited to detect long - lived @xmath14 decays with good efficiency , as seen in figurereftdr20 - 65 . if no signal is seen , an upper limit of order @xmath89 could be established  @xcite . a long - lived slepton nlsp would give tracks with @xmath17 through the calorimeter and muon system . these can be well identified by using the muon system as a time of flight system , as can be seen in figure  [ cmsmstau ]  @xcite . the lifetime can be estimated by counting the number of events with zero , one , and two such tracks , as is also shown in figure  [ cmsmstau ] . it should also be possible to determine the lifetime by looking for kinks in the central tracker , but developing the needed pattern recognition algorithm is non - trivial and has not yet been attempted . if susy exists with masses below about @xmath22 , it seems likely that the atlas and cms detectors should find evidence for it shortly after the lhc begins operation . only a limited number of susy models and cases have been investigated so far , and in all cases the answer has been known . these studies seem sufficient , however , to sketch the broad outlines of an initial program of susy measurements ( assuming that @xmath0 parity is conserved ) :    1 . search for an excess of multijet + @xmath2 events over standard model predictions , which of course must be checked against other measurements . 2 . if such an excess is found , select a sample of susy with simple cuts such as those described above . look for special features such as @xmath90 s or long - lived @xmath16 s in these events . look for @xmath91 , @xmath32 , @xmath92 , @xmath21 jets , hadronic @xmath67 decays , etc . try simple endpoint - type analyses such as those described above . there is of course much more information available , including cross sections , branching ratios , and other kinematic distributions . ultimately one will want to use the first measurements to guide further analyses incorporating all the information . this program will need the full power of the lhc and its detectors . i.  hinchliffe and f.  e.  paige , in _ proc . of the aps / dpf / dpb summer study on the future of particle physics ( snowmass 2001 ) _ ed . n.  graf , snowmass-2001-e401 _ prepared for aps / dpf / dpb summer study on the future of particle physics ( snowmass 2001 ) , snowmass , colorado , 30 jun - 21 jul 2001_.    i.  hinchliffe and f.  e.  paige , in _ proc . of the aps / dpf / dpb summer study on the future of particle physics ( snowmass 2001 ) _ ed . n.  graf , snowmass-2001-e402 _ prepared for aps / dpf / dpb summer study on the future of particle physics ( snowmass 2001 ) , snowmass , colorado , 30 jun - 21 jul 2001_.
the atlas and cms collaborations at the cern large hadron collider ( lhc ) have devoted considerable effort to the study of susy signatures and measurements . 
 this talk provides an overview of what can be learned at the lhc if tev - scale susy exists . 
 = cmss10 scaled 1    by -6.5 in by 2 by -by -8.9 in by 2 by -    to 0pt    --to 8.9 in    = 6.5 in    brookhaven national laboratory    ' '' ''    ' '' ''    to    ' '' ''    ' '' ''    * susy signatures at lhc *    .5 in    * frank e. paige *    _ physics department _ 
 _ brookhaven national laboratory _    _ upton , ny 11973 usa _ 
 .75 in    abstract    the atlas and cms collaborations at the cern large hadron collider ( lhc ) have devoted considerable effort to the study of susy signatures and measurements . 
 this talk provides an overview of what can be learned at the lhc if tev - scale susy exists . 
 invited talk at the _ 
 susy02 : the 10th international conference on supersymmetry and unification of fundamental interactions _ ( june 1723 , 2002 , desy , hamburg ) .    this manuscript has been authored under contract number de - ac02 - 98ch10886 with the u.s . 
 department of energy . 
 accordingly , the u.s . 
 government retains a non - exclusive , royalty - free license to publish or reproduce the published form of this contribution , or allow others to do so , for u.s . 
 government purposes .    * susy signatures at lhc *    * frank e. paige *    _ brookhaven national laboratory , upton , ny 11973 usa _